With all WoW ingame achievements having a Xbox Live counterpart! OMFG!
That would be a smart move for both Blizzard and Microsoft:
Blizzard gets access to millions of potential new customers, Microsoft gets a game into its ecosystem that has proven for more then 15 years it can bind players to itself longterm.
I somehow doubt a monthly fee beyond Gold / GP(U) would sit well with the crowd, though.
They are adding rudimentary controller support in Shadowlands but they said it's purely for accessibility reasons. You can't do actual high end content with a gamepad, though basic leveling and questing would work. An average max level class will have around 15-20 keybinds. Some kinda wheel type interface might work, but they'd have to redesign the game to support slower gameplay I think. Also in an interview recently the game director said there are no plans when asked if the controller support meant it's coming to consoles.
Now, if MS would allow them to release it with KB/mouse "only" (controller still there for accessibility) then I can see it happening. But then there is a myriad of other issues like addon (mods) support which is 110% essential for any kind of high end content, i.e. mythic raiding. This content is balanced and designed around players using these addons. One of the most essential addons requires you to share long text strings with others that contains lua code. You usually copy/paste it from a website.
Console only servers without addons would work, but then Blizzard would need to balance all of the content (Mythic raiding and dungeons especially) separately for PC and console players... and they have a tough enough time balancing the game as it is. Maybe the console version could just have normal difficulty stuff only?
WoW Classic is a much more realistic proposition. The game is much simpler to play, addons are not needed, and dungeons/raids are easy compared to the modern game.
I would love to be proven wrong though. I think playing a more streamlined version of WoW on console would be super chill. I'd probably play it alongside the PC version, which I've literally been playing on and off for 15 years.