If there's any truth to the rumors that the 5DIII will remain in the 21-22 mp range, this makes a lot of sense. The question is whether or not a 40 mp body will offer the balance of resolution and AF of the D800, and the bigger question is price.
I'd question whether many users really want a combination advanced/quick AF, 4-5 fps and high megapixels, the 1ds mk3 and D3x both offered that and had limated sucess. The 1DX and potentially the 5D mk3 seem like they offer more of a balance with boosted ISO and FPS so does Canon need to chase that market anymore?
Personally I'd say the ideal landscape/studio camera would be...
5D sized body with 1D level build/sealing.
ISO performance focused on clean lower settings, max 800-1600 would be enough.
Fewer high quality AF points spaced as widely as possible.
Compaired to Nikon I'd say Canon maybe better equiped to go up directly agenst Medium Format with lenses like the 14mm 2.8, 17/24 TSE's, 85mm 1.2, 70-200 2.8 IS and from the sound of it the new 24-70 2.8 aswell.