The short answer is that I don't know but it certainly seems that way. Read on for the long answer. White is very much turning up in most of the winning decks of late winning a lot of our recent events and placing highly most of the time when not winning. White has undulated in and out of the spotlight ranging from the best to the worst colour. It isn't really white that changed much, rather it was the meta adjusting itself around the fairly stable bar of white. Historically there was not much you could do with white in cubes. Either you played white removal with your blue cards and had a control deck or you played white weenie (sometimes Boros if you failed to get there with a mono coloured aggro deck). Every now and again a three colour midrange deck using white would rise to the top of the pile and give you a whole 3rd way to pack white cards successfully in cube.
It was always the white weenie deck that set the bar, more so even than red aggro. The meta would shift in one direction until the white aggro deck was the best and then it would adapt and shift away from it again for a bit. It was never the case that white was the best deck, just the best suited, and it never lasted. Sure, white weenie has consistently averaged near a top tier deck. But when a deck is pretty dull and linear and it is all a colour has it is hard to get excited about it.
So what is different now? If white is winning surely that is just another meta shift that will sort itself out in due course? The difference is the types of white that are winning and why. It is not just white weenie but white lead midrange decks as well. I have recently won with both a WG and a WR straight up midrange list, something that would have been a laughable archetype five or more years ago. Anything blue or black would have ripped such things to shreds. Further to that, the white decks are getting more interesting and, most shockingly, fun. There are choices to be made, card advantage to be had! Fun, versatile, and powerful sounds like it ticks all the boxes.
So, the next obvious question is why is white doing so well at present? The answer as I deem it to be comes in several parts. The first is the thing I harp on about most presently which is how tempo based my cube seems to be now. This leans into white for several reasons. Firstly it has always had premium cheap dorks which help you gain tempo most effectively. White has also always been the weakest colour for card advantage which is least relevant in a world where tempo is superior to value. Lastly, white has the best removal in cube which gives it all the best tools to fight the tempo battles. If we consider the meta undulating to and from favouring white weenie to be like the tides then this added dimension of the meta favouring tempo or value is like a neap or spring tide on top of the usual movements and so all these natural undulations are lining up. That being said, I am not 100% convinced we will ever go back to a value dominated meta, value will become better or worse but it will still always be tempo that is the dominant metric to fight over. I think that is just the natural result of the increased card pool, card power, design balance and design direction. The game used to be a case of trying to make each of your cards count for more than each of their cards without dying in the mean time. Now the game is about judging how long a game will be and making your cards last that long. There is so much inherent card advantage, late game value, and mana sinks in the game now that it can never go back to being a game so dominated by value in the eternal formats. This is however a bit of a tangent to why specifically white is good and likely a whole article in its own right.
So, the stage is set for white to shine now and going forward. What else has changed? This is more down to the specifics of the cards. There are now a pile of reasonable-to-good cheap white dorks that pretty directly draw cards on an EtB trigger. This is great for multiple reasons and they have mostly all arrived over the last year or so. Firstly it increases deck consistency. When you can squeeze in cheap cantrip cards it means you see more of your key cards, your deck is effectively smaller and more consistent. If you are looking like you might fail to curve you flop out that Spirited Companion instead of the Adanto Vanguard and increase your chances of carrying on making your lands etc.
White is also a colour that leans pretty hard on the creature buff from being the homeland of equipment to the natural habitat of the Anthem. A lot of their walkers and dorks also hand out buffs. With all that going on there is little better than being able to throw out cheap dorks that don't cost you cards. Add into the mix that the main thing white has that is fun or interesting or colour defining is the various flicker effects. White has always had a decent bunch of these and we have seen a couple of pretty good new ones arrive recently. These have really started to shine of late, a big part of which is thanks to this new depth of EtB card draw dorks. Flicker effects are only really as good as the EtB effects on the dorks you have at your disposal and so for a long long time flicker decks couldn't be mono white. Now they can and they can use their flicker to disrupt or gain value as required. Not only are a lot of these newer white EtB effect cards really good in their own right (Solitude, Skyclave Apparition etc) but they helped to activate the full potential of the flicker stuff really giving white that double push. Good removal for tempo and disruption on the one hand or a nice general purpose value generator with your Spirited Companions, Inspiring Overseer, and Ambitious Farmhand on the other. All cards you want to be playing anyway and all working well together.
The EtB draw cards help with value but they are not the only thing doing so. We have some other tools at long last in white that directly or indirectly generate some form of card advantage and it is lovely. The escape on Elspeth's Sun's Nemesis is such a big deal in this regard. It gives you a really persistent and high value threat that ultimately gives you a good amount of reach. Sword of the Realms on the back side of Halvar isn't the most commonly played card but it gives white all the late game it could ever want and has been significantly out performing Skullclamp in white dork based builds. There is Lurrus of the Dream Den as well who can slot nearly into a white deck and is especially brutal when paired with the likes of Selfless Saviour/Spirit and Dauntless Bodyguard, it is downright ugly when a Someone of Runes is kicking about as well! Esper Sentinel tends to be more disruptive than a source of value but there are elements of both. It is certainly a very strong, rounded, and playable new addition for white.
Some more new cards with this disruptive angle include Mage's Attendant, Elite Spellbinder, Paladin Class, and Lion's Sash. These are quite new to white and offer a means of interaction that isn't just removing stuff in play. These tools really help it to fight against the less standard strategies and the more spell based decks. Typically these cards all offer really high option density which is one of the main things white was lacking. Magic is all about choices and so the more you have the better positioned you are to control the game in your favour and use skill to find a win.
It is not just these disruptive cards that are loaded with option density. It is being woven into removal in interesting ways. Solitude is certainly oppressively powerful but the modal casting cost on top of the flash makes it a near continuously interesting choices as to how, where, and when it will be used. March of Otherwordly Light offers a similarly interesting set of choices as to sacrifices cards in hand for mana returns.
The last big thing I want to discuss about white is flash and instant cards. These are huge in a number of ways and white has some of the best, especially when it comes to tempo. Flash lets you gain so much more value and safety with your cards, not to mention being one of the biggest things you can have as far as option density goes. They can be left to the last minute so as to gain the most information or dodge disruption from the opponent. They can come out at a surprise moment and mess up a combat step. Flash cards are to be feared and that gives white a real edge. Get ahead on the board and then put the fear of god into the opponent with mana up and cards in hand waiting for them to walk into something nasty. That used to be something you needed blue to help with but now white can pretty much do it by itself. Avacyn is a house who wins a whole load of games and is one of the few older threats that seems to be getting better with age and holding up well in the face of current power creep. Restoration Angel has always been one of the best flicker effects in white and like Avacyn has been getting better of late not worse. This is mostly down to the quality of the EtB dorks we discussed but just being a flash 3/4 flier get s a lot of work done.
Then we have the big new name of Wandering Emperor, the only flash planeswalker and an absolute beating of a card. Combat trick, removal, board presence, threat, ability to overextend without fear of getting ruined by mass removal complete with the ability to navigate around countermagic better than most other such cards. Add to that Force of Virtue, Cathar Commando, Settle the Wreckage, Solitude again obviously.. all more examples of powerful, versatile, and new flash cards that have a big effect on the game.
As white was so far behind the other colours in terms of card advantage and card quality effects they gained the most from the introduction of the more efficient artifact offerings for such things. Smuggler's Copter is obviously busted in all the colours but white felt like on of the biggest beneficiaries. Cards like Mazemind Tome, Reckoner Bankbuster, Retrofitter Foundry, and Treasure Map all offer more to white than they do in most other places and have been pretty big in pushing the midrange white builds. Even the utility land situation helps white more. Horizon lands are great but more great for white than other colours in exactly the same way the artifacts are. Castle Ardenvale and Cave of the Frost Dragon further help this but from a slightly different angle. One of the few things white can do is find plains and so cards that can loot, or turn excess mana in to something useful, or just cash in lands directly as per the Horizon cycle, all work especially well for white. Even the more aggressive side of things are getting interesting cards that give options and means of turning mana into value like Usher of the Fallen and Paladin Class.
So there we have it, a lot of new cards and types of card that are helping push white in a favourable meta. Powerful removal, option rich cards, high tempo cards, more good natural synergy cards, and most importantly of all - the cards that are helping plug the holes previously restricting white decks. So let us finish with a nice little example list of a midrange mono white deck packing as much new stuff as possible and looking highly competitive.
March of Otherworldly Light
On Thin Ice
Winds of Abandon
The Wandering Emporer
Settle the Wreckage
Field of Ruin
Cave of the Frost Dragon
Eiganjo, Seat of the Empire