Please explain why MP is all that matters.
Of course it is not *all* that matters. But it helps with cropping when using a prime and macro shots, changing aspect ratio and different framing in post-processing, easier framing while shooting because cropping doesn't let you drop into too low mp regions.
Improve the IQ, Improve the NR, Improve the ISO across the board and do it without getting MP crazy.
With the 5d3 in the same mp range than the 5200, it can hardly be argued that 24mp is crazy, at least if Sony's sensor tech keeps delivering and the noise (at least when downsized to 18mp = Canon aps-c) and dr are within reason.
I don't think we'll see much of a 650d soon if Canon was as surprised by this as they seemed by the d800 - with the aps-c line being made for dlsr first-timers that don't have a lens zoo to keep and can easily "jump ship", imho the 600d is toast. Apart from running magic lantern, that is.