It seems that the megapixel war is official, as Nikon Rumors is reporting a 36mp D800 is coming in the next 30-60 days at a 99% probability. The rumor has been there throughout however it missed the date of announcement, but more importantly the camera seemed to be a reality.
The relevance of big megapixel Nikon D800 could be the expectation that Canon will response with a new SLR at the same niche. It seems that Canon is just waiting for Nikon to go with announcement to decide how to proceed.
If Nikon will be able to ship the new D800 this year, Canon will have no space but to answer back with a new SLR. Though the theme could be big megapixel camera, Canon could go for normal megapixel, however with excellent high-ISO performance and interestingly a full-frame camera.