World Of Warcraft: Rest XP In The Expansion

From The Official Forums:

If you are already level 60 and have been for awhile, you will not start with rested experience. However, as you begin to level from 60 to 70 (provided you have activated the Burning Crusade expansion) you will begin accumulating rested experience again the same as you normally would. So if you've been used to camping out wherever and whenever, you might want to work to break that habit and start camping out at Inns again.