Q: Do you need to own the expansion to play with friends who have it?
A: There will be many aspects of the expansion that are available to all players. However, in order to experience certain content, such as Outland, or be able to play as one of the new races, players will have to purchase the expansion.
So, has there been any new word on what exactly is available without the expansion? Or rather, which features are truly exclusive to the expansion?
UPDATE: We at least know that you cannot reach level 70 without the expansion. Read: WoW BlueTracker