Canon's 5D MK III is all set, and Canon knows what the Nikon d800 will be. The only question in my mind, is will Canon resist the temptation to pile on MP, or do something more modest. Those samples of D800 images at higher ISO's look horrible, hopefully, they were from a prototype and will be much better for a released product. Right now, Nikon fans are really screaming on the Nikon Forums.
Its always possible that the images were planted, just to see what the response was, and that a backup plan is in place.