I think there will always be WoW. It's such a popular game and they always come up with new games/updates and things like that. As long as people keep buying WoW they will continue to keep it going.
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.
I still remember when it was announced back then, half a year later there was a leak from Vivendi that there should be 6 extensions and nothing more after that.
Now comes the 7th and as long as Blizzard can make money on the game, they will keep developing it
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.)
There will always be a community for it i believe, if blizzard will keep hosting it is another topic. I believe so, to many die hards will keep playing