Like I said before. Canon's "Answer" to the Nikon D800 (and future D900, and the Sony A7R) will come as a big bulky elephant sized 1D-body, with a price tag that most people can't touch.
Ok, then...but what are Nikon and Sony's "Answers" to the 5DIII, which has outsold the D800 and will vastly outsell the a7R?
Why do people think Canon needs to play Nikon's game? The D800 was Nikon's attempt to play the game by Canon's rules (we'll see your 8-9 MP increase, and raise you by another 14 MP), and Nikon lost.
I think the numbers argument (BTW, do you have the quantities sold for the D800 and the 5Diii?) is somewhat specious. There are many other considerations than just mp count. I, for one, would have jumped to the D800 if 1) Nikon lenses were as good as Canon and 2) I hadn't had alot (to me) of money tied up in Canon lenses.
Also, I don't think that the high megapixel camera is simply Nikon's game. There are some of us out here that think that a high mp full frame have advantages over the 20 mp variety in terms of cropping or larger prints, AS LONG AS the higher iso performance is reasonable.