uh. 6000 series, vs 5870... hmm...
Listen to me, we are relitively at a time where graphics wont get much better. If you are the type of person who wants the play the most high end games, I would simply get a 5870.
Honestly if you want something that can run high end games, crysis is pretty much your only worry. In otherwords, its pointless to wait for something that wont drastically increase preformance vs a 5970 or 5870.
Bottom Line: Graphics arent going to get to much better. Get a 5870.