They've already tried this before with their own games and that hasn't worked.
I just don't see them trying once more to pull another fuck over move and force everyone to use their already crappy storefront on PC. Like you can force your Xbox gamers to do whatever tune you jam out with, but PC for the longest time has done it's own thing whenever it wants to.
I'm a fan of ES and Fallout and yeah, I'd stop buying, because I'm not going to just "give in" like some spineless normie. If they stop selling those games on Steam/GoG, I'll just buy from someone else instead, it's that simple.
Consoles take 30% as well as other storefronts. Also, MS isn't likely to give up Steam for a chance at trying to force people to using a storefront that not many like using in the first place.
I don't see it happening, I'm sorry. Much as you want to harp on about the 30% (known only after Timmy boy harped on about it, thus random folk are now doing the same), Steam is still going to be around and is still going to see big games sold on it.
If the game is available steam. For $60. And the same game is available on gamepas, same day and date, and you can download it, "just as you could with steam" and play it. What would you do?
Play for $60? or play for $10?