According to the game's lead writer Mac Walters, Mass Effect 3 will be returning players to the original game's Citadel. “There was a Mass Effect 2 plot that was a kind of callback to the first Mass Effect that was going to be on the Citadel, and we cut it,” says Walters, “but now it's made a resurrection in Mass Effect 3.”
"I definitely have some writers who want to try something else, to move on. For me, personally, it'll be over seven years of Mass Effect - I have a soft spot for the universe, but it's easy to get a little weary. But I'd be much more sad if someone said "yeah, you can never do anything Mass Effect ever again," and no one's ever said that to me specifically. I'd rather take a break, then come back to revel in it again and enjoy it", Walter added.
Bioware also confirmed that you will be able to take on Citadel missions that were originally slated to appear in Mass Effect 2.
Mass Effect 3 will be released March 6, 2012 in NA.