Today.
By the way, anybody considered the idea that Thrall is back because they'd like to pay homage to Warcraft 3: Reign of Chaos, and its Exodus of the Horde campaign?
It's a long shot, but pretend that Blizzard's going to let the Void conquer Kalimdor and the Eastern Kingdoms in 11.0. Some stubborn people decide to remain, whole others leave for a new home.
Thrall leads us across the sea once again, until we discover Avaloren.
Once there, we find Mount Even-Hyjalier, and the Super Barrens, and Stonetalôn Moüntainz. On a serious note, it might be a new home for the Horde and Alliance in the making, though.
It's an alternate explanation to all the HD models of guard towers, wyvern roosts, taverns, etc. instead of a revamp.