I don't buy this argument that an improved 5D MkII replacement would obviate the need for the 7D. The market for the 7D should be purchasing this camera either for what it offers in terms of 'more pixels on target', or for its lower price. If potential 5D series owners are buying a 7D because they are put off by the 5D's poorer AF and slow speed, then surely Canon are losing potential profits?
If the 5D MkII replacement is to stay low(er) megapixel, Canon will need to do something to sell it over buying a second hand 5D MkII and I don't think that an extra stop or so of ISO will cut the mustard. It would make sense to me to ramp up the AF specs and continuous burst rate, as there are many other ways to 'hobble' the camera for pros. Even having the 1D X's AF system would not guarantee 1D X levels of performance, especially if the '5D MkIII' didn't have the same processing power. They could also make the buffer smaller than the 1D X (like Nikon did with the D7000), which would also put off serious sports shooters. Next, they could remove dual memory card and ethernet support, further discouraging professionals.
Professionals who make their living from their photographs are generally quite conservative, they rely on their camera behaving exactly as they expect it to in order to get their shots. If they've owned a number of 1-series cameras it is unlikely that they would easily be persuaded to 'trade down'. Whilst most of us are feeling the squeeze economically, a new camera body every four years is not exactly the largest business expense for those that truly make their living from photography.
