The mother of all rumors

Is the market really crying out for a D4x (or successor to the 1Ds3 for that matter)?

Very few lenses are up to the task at 36mp, let alone if they go beyond that. The D800 is diffraction limited just below f/8 so your range of apertures to resolve maximum detail is quite limited.

Lastly, what areas can they improve to justify a substantial premium of a D4x? The D800 already has pro AF and decent weather sealing and you can probably afford to carry a backup for less than the price of a D4x.

Canon all but killed off the 1Ds with the 5Dmk2 which was a huge success and Nikon has simply copied that strategy.