I am assuming that they'll do it a few months after the expansion ships. Then again, the leveling curve in WotLK never seemed that bad to begin with. I think that I was completing levels in about four hours just running quests with my shaman (rested XP). But they have made clear that they focus on the max level for all balancing and game play, so the faster you can get there, the better. March or April of 2011, maybe?