I would be happy if the 5DIII had 1D4 AF and 12800 iso.But, it won't. It will be lucky to have 7D AF.
I agree that 5DIII would be lucky to have even 7D's AF. Here is why:
5DIII will be aimed at studio/landscape photographers. Of course they deserve a decent AF system with their camera, say one that is between 60D's and 7D's AF. But not more than that or Canon will shoot themselves with their own weapon. 1DIV's AF is way too advanced for a camera that won't even need it. This would also mess the Canon lineup. 1Dx sales could suffer, 7D's or 7DII's sales would suffer although they are aimed at totally different markets. Heck, even 5DIII's sales would suffer because of it's increased price (highly advanced AF would obviously cost more). Why would Canon take such a risk?
They would not want to put all killer features in one camera and sell it for $2500... Why would they? They want you to buy the flagship model for that, and for a price. They would want to keep a good distinction between all their cameras to ensure that they all bring in the maximum cash. Which I think is only fair given the R&D they are putting in their different products. I know these cameras are already different in so many ways (sensor size, pixel count, low-light capabilities, burst shooting, etc) but AF system has always been the key feature to keep them really separated.
People expect better AF in 5DIII and right so, 5DIII will have better AF. Because Canon would want the 5DII users to upgrade to the new model and they know that only better IQ/low-light performance in the new model won't cut it for many of us. So a slightly better AF is all they will offer.
Just my 2 cents...
Granted... if they want to stunt the 5d3, remove the video capture features and let people use the 60D or 300C etc for Video... Give us a decent Still Camera with at least 5-6 fps, 5AEB bracketing, decent AF and ISO... Hopefully this is a fair trade-off.