1.) I'm going to have to disagree regarding diminishing returns. All the talk about lenses and sensors not being able to produce good IQ at high pixel count has been going on since the launch of the 5DmII. My 5DmII was shipped to my house 1 week after the launch date. I immediately found all those fears to be false. What I'm trying to say is that all the "Know-it-alls" cast judgement about whats possible and not possible before even trying the camera based on theory.
2.) I hate being told that "I" don't need high pixel count because I won't ever print pass __ x __ size. I hate being told that what "we" need are more A, B, and C. Everyone is different.
3.) As I wrote on another thread, I do fashion, landscape and product photography I can definitely use more megapixels. No. I don't need 80MP. When the count gets that high I would agree that the lenses we have right now and the sensor size we're using PROBABLY won't be able to manage an acceptable image. However, I think 40+ MP is still within range seeing that my gen-1 24-70 f/2.8 and 5DmII produce tack sharp product images. I'm not even using an L Prime and the images are already too sharp (well its never too sharp for product photography).
If possible I'd personally would like a 40+MP Canon DSLR with a better AF system than my 5DmII and 4FPS is fine for me. If they want to squeeze in more that's fine.