They will just update the current game(speculation). Via engine overhaul, plus a lot of players have sentimental value attached to their accounts/characters. So unless this new WoW 2 allows for account/character data transfers to the new game. I can see it being DOA if it doesn’t, seeing as alot of players would quit over this.
I personally think WoW 2 wont happen, instead they’ll just keep updating the current World Of Warcraft.