Scott Kelby makes a point - the D800 isn't the true successor to the D700, in that breaks form - it's less about sports or action than the D700 or the 1DX or the 7D. http://scottkelby.com/2012/jumping-the-gun-on-the-d800/?utm_source=twitterfeed&utm_medium=twitter
How Canon responds? Well, the 7D/5D MkII hybrid sounds about right.
To play the devil's advocate:
The cinematographers will be disappointed if there aren't improvements like the D800's.
The wedding folk will call for pitchforks if their low light needs aren't satisfied
Landscape folk are wanting a MF in a FF body, and general folk might complain if it's higher priced, above the current 5D Mk II, to make (more) space for a 600D, 60D and 7D replacement if needed.
What are they responding to? The MP count, the video capabilities, the AF/AE/Face recognition/FX,DX capabilities?
I don't see why Canon can't come out with a higher priced 5D replacement. The 7D price went down quickly, the 5D MarkII has had a gradual decline, but I don't think either model sold new is going to go any lower than it was a month ago.