I don't agree that if the 650D/70D had more megapixels than the 7D, it would totally destroy sales of the 7D.
The 7D is a "luxury" APS-C camera that is a joy to use. Also, it has AF Microadjust, which the other 2 cameras probably won't. And it does 8FPS.
I took mine out yesterday for the first time in a while, with the 24-105 L, having been doing film photography for the last couple of months. I remembered again why I love it so much!
Wandering slightly off-topic for a bit:
Frankly, the quality of pics I'm getting from the 7D totally destroys what I'm getting from film - ALTHOUGH I am suspecting issues with negative scanner or its software at the processing shop I use. I might look into that more later. Currently the 7D pics have much deeper, richer colours, and more dynamic range most of the time (!!!). And better resolution; the film scans are grainy; again, this surprises me a bit.
I shoot jpeg (!!!) and NEVER do anything in post. That is policy. I'll take the same shot again and again until I'm happy with the exposure and composition, and when I'm happy with it, that's it. And that often works very well for me. I like to get it right in the field, using the camera. Admittedly I'm just an amateur, so there are no other pressures on me. I get my pics printed at 18" x 12" which works out at about 11.5 pixels per mm, and the resolution at that size is fantastic; there's more there than the eye can see properly, really. So my 7D gives me what I need and I'm so pleased with it.
I will be buying the 5D3 pretty much as soon as it comes out, and keeping the 7D as a second body.
My reason for going full-frame is so that I can shoot in near-darkness with low noise, and to give me better DOF control, i.e. better bokeh for a given composition.