A 16 megapixel D800 will be awesome, Seems like Nikon has been listening to Canon owners.
If you put the pixels from a 1D4 onto a FF-Sensor you'd end up with a ~30MP(give me a weaker AA-Filter instead of that extra 20% pixelcount ) camera that comes with really nice high ISO and considering moore's law enough power to keep the 10fps. Wouldn't be to bad for a high end.
OTOH if one thinks of focal plane phase detection AF - no more blackout and associated delay times or AF adjustments, no limiting mechanics. Crop down to APS-H or use enough readout channels/good binning patterns - 60fps at 4k resolution or 120fps at HD while retaining full AF would be imaginable.
Just a pipe dream, but it would make the 1D(s) split obsolete.