I don't think this is very likely. The D3x was not significantly faster than the D800 and very few Nikon photographers would be interested in buying a more expensive body for one fps. Besides, the limitation in terms of speed is probably with sensor readout and is not likely to be easily lifted.
A D800H based on the D4 sensor is also pretty unlikely because the D800 appears to have high ISO performance very close to that of the D4 up to ISO 12,800 which is reasonably the highest one really needs for all but sports applications.
My view is that the next DSLR announcement from Nikon will be a D7000 dot upgrade to be followed by a D400 that could either be a DX high end or FX low end body.
But frankly, the D800 is likely to be all we'll need for the coming 5 years if not longer.
Add a few mandatory missing lenses and that's it...
Cheers,
Bernard