Mid-range 28nm 7870 offering 6970 +10% (my estimate, no source) performance at half the watt (heat/noise) and a ~$200 price point is a winner. AMD/ATI seems to think they can release it in early December and they have been claiming such publicly.
Just to reiterate, there's no reason to doubt ATI devs when they have made public statements regarding 28nm launch.
If its anything like their previous launch, the 7870 mid range is going in first then come the 7970 high end to follow. The only question is, whats the time gap? If its one month, that's not a big deal at all. If its a few months, its going to give NV time to release their 28nm stuff at the same time.