All this talk about AF systems again, so I'm sorry to grind on my personal favourite organ about this...
The 9 cross type AF system from the XXD line would have been acceptable on the 5D MkII, but Canon were either in a hurry, being cheap, or were genuinely taken by surprise by the D700's AF system. The 5D MkII was redeemed by its sensor and its video capabilities. The world has now moved on and Sony are in the full frame game as well; if Canon continue to cripple th 5D series, they will lose this section of the market to the competition. Unless Nikon downgrades the D800's specifications from its predecessor (when was the last time that Nikon did this?) and Sony decides not to bother including the A77's technological advancements into a forthcoming FF SLT camera, the '5D with a new sensor' approach will fail. If you're seriously looking to buy into this segment or upgrade your current 5D model, what would this strategy say to you: "buy a Canon, we're second best"? This reflects down the whole product range, because consumers tend to look a level or two up the product line when they are purchasing to determine the brand's image.
Canon must risk their 1D X sales by upping the specs of the 5D MkIII AF system, many people won't actually need it most of the time but that's not the point. I live in the UK and my car (like most these days) has air conditioning, which is great for the few days a year I actually need it. Try selling people anything other than a base model without A/C.
Canon are competing in this market on a differentiation strategy, if their sensor isn't a lot better than the new Sony FF unit, what will Canon differentiate on? In my view, the 7D's AF system is the bare minimum for the 5D MkIII; let's not forget that the frame coverage of the AF points would be virtually the same as with the 5D MkII (just higher density). If Canon are unwilling to go the whole hog and fit the new 61pt AF system to the 5D MkIII (and 7D MkII), they should develop a new AF system for these cameras; how about a 39 pt "low density reticular array".