I will admit that it's possible that the 5DIII will use the 7D-type AF, but you seem to be suggesting they'll re-use the actual AF sensor from the 7D, without compensating for the larger frame. If they compensate for the larger frame, it means developing a new sensor. If they don't, it means the 5DIII would have more AF points, and better ones, but the area coverage would be even less than that of the 5DII, as you can see in the attached image (5DII in blue, 7D in black). Canon has expressed a willingness to take things away from new models, as discussed above with f/8 issue. But the AF area coverage of the 5DII was already not a strong point. When they released the 5DII, they touted the fact that the horizontal point spread was the same as the 1DsIII, conveniently ignoring the fact that the vertical spread was a full row shorter. The 7D's AF sensor on the 5DII would mean the loss of a horizontal row, as well.
I was aware of the implications of using the 7D AF system in a future 5D, but I've never seen it drawn as well as you have done, so bravo. I don't think that Canon would bother to design a new full frame version with a greater spread (although I hope I'm wrong). AF point frame coverage vies with the lack of cross type sensors as the reason for the inadequacy of the 5D's AF system, even for people who don't shoot action. You've previously mentioned the problem with the focus and recompose method of focusing at large apertures. But marketing loves numbers and 19 is better than 9... I wouldn't like to make statements about the 1D X's AF system before it's been released or without any information about the design decisions made. I personally favour the trade off explaination for the lack of any f/8 capable AF points. Canon would have to be pretty confident to drop a good marketing differentiator just to try and sell people longer lenses; it's a hazardous enough move asking their customers to change formats without adding further risks to acceptance. Having said that, many companies have made stupid decisions like this in the past!