That is a possibility.
Still there is a large bunch of people who whould happily buy a harcover book from an established company, which also has a range of miniatues to go with the theme. I'm actually surprised how reluctant people are to go after T9A, 9th ed, etc. I'm a little bit troubled about these legacy games, none of them seem to be growing after the initial push and goodwill.
KoW is in the same boat despite being supported by a company and a full miniatures line: I don't see it growing after the hype of the 2nd ed. Why? Because the world of Mantica is not a thing, the armies are not 1:1 Warhammer, and the gameplay and especially army building are different from any Warhammer edition?
I'm actually participating in a campaign that runs on the 8th ed by the book, because that's what the organizer thinks works best. (It doesn't. 8th was and is lacking in inner and outer balance compared to the earlier editions, ETC and Swedcomps, and more modern fan-editions. It's basic gameplay is sluggish and some of its rules are stupid. It cries for a good 8.5 adjustment or a full 9th ed.) The other day I scanned the second hand market for 8th ed army books, and it seems they have become quite valuable again. People want them, despite there being a free and fine-tuned version of the 8th, namely T9A (1.1).
After a two year hiatus, we are now witnessing 7th ed games and even tournaments organized. Not as big as T9A, but certainly challenging the idea that T9A would be the present and future of this kind of gaming.
If it's not about the game, it could be about the fluff. A good number of people mostly want the fluff, i.e. Old World. They could probably take AoS style mechanics, if they supported square bases and the story of a living Old World. I know I could, because the hobby for me was and is predominantly about the models on square bases in the Old World. A reason why I both like KoW but also find it lacking the right feeling.
I'm fairly sure GW could sell at profit a couple of books about a sort of historical AoS, where the Old World hasn't died yet, and where the armies assembled in ranks and files. Like if 30K was a great hit, maybe Before the Age of Sigmar could work too, as a one-off or periodical side project similar to the Specialist games. They could do a small range of new models and see if they sell or not.
Then again assembling big miniature armies for a single game (or game type) seems to be last year, unless playing historicals. Games that are meant to be enjoyed among friends tend to be skirmishes with a reasonable number of individualized miniatures. You see it everywhere. The number of people who really are dedicated to an army level game is likely dwindling, and I don't see many starting this kind of hobby, even if T9A, 9th ed and KoW make it actually free rules-wise.
I'm not hopeful about GW retunring to WFB. This is more about the scene, and what people do and don't do in the scene after GW killed the Old World.
-Z