In all honesty the resolution of the D800 hasn't really blown me away, both it and the 5DII seem to be lens and skill limited a majority of the time. I print most of my stuff in the 20x30 to 30 x 40 range and the difference in resolution between the two camera's just isn't noticeable. However, the difference in color tone and range is clear as day, which really surprised me because I loved my 5ds color rendition.
If Canon does release a high MP camera I will be shocked if it can hold a candle to what Sony and Nikon have created with this beast of a sensor. We shall see though. I would love to see a solid high MP high dynamic range camera to attach a 17mm TS to.
Skill limited I can understand, but lens limitations will not be an issue for long. Yes its going to be expensive, but these higher mp sensors have triggered a massive redesign programme for all the major players.