Canon Rumors is leaning towards 28 MP's in the 5DmkIII. This puts it close to the FF version of the 40D sensor IIRC. IMO this looks to be the sweet spot for now.
I do not think Canon will want to offer worse IQ or noise or banding then the current 5DmkII.
Canon seems to put newer ideas in lower priced units to beta test these features and work the bugs out. Then they put them in the top of the line bodies where there is far less drama and at those price points rightly so.
Here is my wish list.
7D AF and AF points.
5 FPS and 5 exposure bracketing for -2,-1,0 and +1,+2 shots for HDR LANDSCAPES. I see this body as a portrait and landscape body and the 7D as an action body.
7D weather sealing but PLEASE give us a weather sealed shutter button and wheels. Remember it is a LANDSCAPE body?
Dedicated movie button like the 7D and more FULLY programmable buttons.
4,2,2 video would be lovely and eliminate the banding issues is a must.
Tie the histogram to the RAW file.
I wish Canon would give us the absolute best chimping feature. Take the pic and the rear screen shows the pic zoomed to 5x or 10x (your choice)on your AF point so you know in a instant how your focus was. No need to press a mess of buttons and stopping your work flow.
Am I the only one who gets this last feature?