I know its kinda soon to be talking about this. And no one really knows anything yet, but its kind of fun to think about them. The 8870 and 8850 have already been leaked. They seem to be amazing for their price. I was thinking about even waiting for one of those rather than getting a 7950/7870 right now. Just wanted to post on a topic I thought was interesting.
http://videocardz.com/34981/amd-radeon-hd-8870-and-hd-8850-specifiation-leaked
Kind of an old article. But gives you an idea of the next gen gpu's