There's already a situation to contend with there thanks to SteamDeck and the boom of handheld PCs. (However, WoW isn't on Steam and doesn't run Linux; sideloading is an option but it's probably not a hot issue for Blizzard just yet. Also Deck and most portaPCs have touchscreens, despite the interface being miniscule, so that goes beyond just a controller.)
WoW mods like ConsolePort and AzeriteUI and DynamicCam and Immersion help give the game more visibility for what would work in a console version. It's still a potentially confounding number of keystroke combinations depending on how you set up your macros (although console MMO players are probably used to having a bazillion combos to get to all their spells and commands,) but Steam Deck players have been giving it a thumbs-up as a way to play.
(Also, BTW, Xbox allows for K&M in supported games. Still not ideal though, since most would be playing Xbox on a couch instead of at a desk.)
What you don't want is for Blizzard to "dumb down" the gameplay to meet the console players' access level, and that's a fair concern. FFXI and FFIX were both made for simultaneous console/PC play, so while the player base doesn't seem to be miffed over being mixed there, they never had it different. Not many other MMOs have come over to console, those that have have AFAIK still focused on their core PC community and graft on console controls as best as possible to mixed results, but WoW is such an institution that any changes would be questioned, while the prospect of making money off the console space now has a higher demand from the owner (not that Activision Blizzard wouldn't have liked having that money added to their take.)
WoW though is so old and operated on so many different levels by players of widely varying skills on vastly different PCs and with a range of mods applied, and with long-term players so intrenched in their processes and groups, I'm kind of surprised there's so much pushback of potentially more players. The game has growing pains either way every time it draws a new player base in, and it's up to Blizzard to design well-rounded mechanics so that everybody can enjoy at different phases of play. There are generally ways of playing with people you like and are at your level, and if you're raiding for itemlvl 9000 weapons, I'm not sure why the players you'd surround yourself with would suck at the game with whatever control device they've decided to play with?
I generally think this is still never going to happen (...what's the rush?) even with MS eyeing the possibilities, but I'm not seeing that this would ruin WoW if it ever did. It would just have to be done well and mindfully.