Those are 5850 6850 7850, but as you can see the 6870 would beat a 7850 idk how, but according to their review it would. Only the 7950/7970 in this new series seem to be mildly impressive. The 5xxx series continues on.
another review that is not relevant with a 7770 but, you can expect better performance of the 6870.
6870 would outperform the 7770, but due to the fact its built in the 40nm architecture compared to the 7770's 28nm, it would theorectically have more power usage and slightly higher temperatures. (theoretically means im too lazy to check)