In all fairness, it would have much more of a problem than GW2 has. Assuming there's no redesign of the game, the only thing WoW would have for max level characters to do at that point is heroic dungeons, which are cleared in ~30 minutes or less each. You could argue that exploring, questing et cetera would still be available, but WoW has never been a game that encourages that, aside from arbitrary points in your achievements tab. It's always been more a case of "this is here, and you could do it, but over here in this 10/25/40-man instance is where it's really at".
GW2 and WoW was designed differently, and it makes no sense to even try to compare the endgame of the two.