Correct me if I'm wrong, but I just did some quick calculations and it looks like:
7D sensor at 18 mp = 46 mp full frame
50D sensor at 15 mp = 38 mp full frame
1D IV sensor at 16 mp = 27 mp full frame.
So, it seems to me that if Canon decided they really need to bring a higher megapixel camera to market quickly, they don't have to reinvent the wheel. Could they just upsize one of their current sensors?
The only one of those sensors that i would be happy with the IQ from if it were upsized with no technological advancement is the 1D1V at 27MP
if however they got ontop of the 7D low iso noise, high iso noise and general softness (this is relative softness mind you i'm not saying its marshmallow soft for all the crop lovers out there) fact is the 7D IQ needs improving and I think perhaps a touch of the new sensor tech can give it that lift it needs but of course the crops are going to need a MP jump to beat sony.
I've said I think they will try and 1 up sony with 27MP (just a guess) now if you make that Full Frame you get 69 Dude!