World of Warcraft Interview

Talking to VG247, lead designer Tom Chilton confirmed that World of Warcraft will expand further into known Warcraft territories.
(We actually already have ideas on how we're going to expand on that in the future,) Chilton told us when asked if more land was going to be added to the game.

(Certainly, [a lot of] the major landmasses that we talked about heavily in previous WarCraft game have already come to fruition, although there are still areas of the game that we've talked about and set up story-wise that we haven't revealed yet. So there's definitely more to go.)