The problem with Nikon is that while the D700 "crushed" the 5dmk2 in terms of AF specs, it also crushed their own D3, which is something Canon will not do, they aren't going to over spec a 5d body to kill sales of their 1 series bodies.
This is why Nikon appear to be taking care to place the D800 in a different market position to the D4, as a slow but high resolution camera as opposed to a high-speed and low noise camera.
And Canon seems to be doing fine when it comes to share. Forget sales figures, because there isnt a breakdown between models...Just for comparison I went to B&H and had a look a the number of reviews for the 5dmk2 compared to the D700 (not scientific but fairly balanced way to look at it) and when you combine the reviews for the body only, and kit you get about 2100 reviews for the 5dmk2 and for the d700 there are just over 1000. Sure its not sales figures but I would venture to guess the rate at which buyers leave reviews is not 1:1. I dont think the d700 "crushed" anything and therefore Canon would rather have their own house in order because what they're doing works for them...share-wise and otherwise.
Forget looking at past sales figures, that's what Kodak did and it told them there was nothing to worry about!