I think WoW coming to consoles is a matter of when not if, but I don’t think they’ll include the game’s subscription in Gamepass. Right now the base game is free to play up to a certain point, so including the game in gamepass wouldn’t change that and might convince more people to try it out.
Having said that, if they included the subscription with GP Ultimate, they could maybe then offer another monthly fee that includes special mounts, pets and transmogs for those that want those things. It would also probably lead to more items for people to straight up purchase. It would be a delicate situation as the fanbase is very sensitive to change.
If WoW does come to consoles I could see them doing the console version sub being included in Game Pass but not PC. I think it’s a pretty tough ask to get people to pay for online use on console then tack on an additional $15 per month sub to access 1 game.