That's what I expected... at least the last ATi cards launches, the NDA ending date was the same than official release date, if I remember correctly. I'm not sure about the new cards NDA ending date, because I've seen different dates here and there (16th, 22th...) but all of them seem to be in September.
So I think that the cards will be released this month :yepp:
As long as they use some faster memory than last time (and if they're going to use only GDDR5 this time, at least that will be the case for the 850 model) they'll be fine, I think. I think that memory bandwidth was more than what they needed with HD4870, because it had 2x the memory bandwidth of HD4850 and if it was fully used it would have bottlenecked more the performance of the 4850.
Even if they use the cheaper 3600MHz memory that they used last time, it would be double the bandwidth for the 850 model (even with the same memory interface, and for a doubling of processing units), and they could use faster memory for HD5870 (indeed, I expect they do, to differentiate more both models).
So if using GDDR5, at least the 850 model is going to have double the bandwidth which seems appropiated if they are really doubling the processing units number, and probably the 870 model will need less increase than that.