I've read some Blizz guy say something about 10 expansions minimum.
The truth is, as long as the game stays profitable (and it surely is, even if it's not as ridiculously profitable as some years ago) Blizz will continue WoW.
World of Warcraft will surely go the way of the Dodo someday but here is another example Ragnarok Online (look it up) there is still an active community and all but the majority of player is in the Private Server scene and that game is over a decade old. Maybe at that time WoW will be the same who really knows with Blizzard and all.
Blizzard will eventually find new aspects to adapt it for the new incoming generations of players and for the market that will be in the next 5/10 years, they cannot end a thing that generate tons of money, if WoW will die is because WoW will kill itself and become obsolete to the new generations, because the old generations will not play forever.
If Blizzard manages to leave the hotkey+tab battle system behind and evolve the game to something greater, then yes.
Tab+Hotkey cycling is so 2000. With sophistication and advancement of game engines and software development techniques, there's no longer a place for tab hotkey battle system. Everyone is moving towards action and real hitbox system (Monster Hunter is an exemplary pioneer, along with Dark Souls, Bloodborne etc.)