I see them getting rid of the 7850 1gb and sliding in the Bonaire into the 650 Ti price, maybe slightly cheaper, and then the 7850 2gb can slide down in price a little as the next round of price cuts take effect.
I also don't think the 7790 will have 896 units, it most likely would have 768 shader units. Shades of what AMD did between the 5000 series and the 6000 series (5670 had 400 shaders, 6670 had 480, etc) - just add another increment of shaders as the process technology at 28nm gets better.
I remember seeing rumors of a 768 shader radeon 8770, with 128 bit, maybe 192 bit memory, and suspect that the 7790 is the new name. This way they can just test out the drivers for GCN 2.0's without too much bad press as to their halo product having bad fps, and then when the GCN 2.0 drivers are optimized bring out the 8000 series in late 2013/early 2014.