This is my POOMA-analysis of this whole thing:
The D800 is a completely new thing for Nikon. It's a huge departure from the D700 and a leap towards the 5D II. More res, lower FPS, aimed more towards video than previous models.
Look at what Canon did with the 5D II - awesome FF-resolution at a fairly low price, whereas the D700, from what I've heard said by the Nikon shooters I know, prompted people to get rid of their nikon D# or forgo it because the D700 pretty much preformed similarly with the battery grip. You could say the 5D II did the same to the 1Ds, but for people needing speedier and more precise AF the 5D II was newer a choice. The 1D was left alone, never touched by any other Canon, and probably the best seller of the 1D products anyway.
So essentially they are forcing people towards the D4 if they want speed, fullframe and lower res. Pretty good choice, I guess.
As for the 5D III having lower resolution than the D800, well, only time can tell, but I'm fairly certain that It'll be closer to the resolution of the D800 than the current 5D, I'd find it extremely odd if the performance of the 5D III comes close to the 1D X. As for people jumping ship, well, I'm also fairly certain that the ones who'll do that are the unfaithful customers anyways, that aren't locked into a large collection of lenses. The camera has to be a massive disappointment if people switch in large numbers (like the 1D III that had people, hell, whole agencies and newspapers, switching to Nikon).
As I said, pulled out of my ass.