Apparently the D800 IS what Nikon thinks D700 shooters want.
Certain commentators like Thom Hogan agree, he says we just don't realize it yet.
I think with the D400 it is just an odd man out situation. Nikon surveyed the market and just doesn't feel that is where they can maximize their profits. They will certainly sell a lot more D7100s then a 600-800 dollar more D400 IMHO.
What DX shooters should really be pissed off at is how Nikon has all but abandoned the DX lens market by and large.