Not really a rumor, just a prediction for Nikon D400 (this is why we have Page 2). I am not sure what is "FX format with a DX sensor" but hey, what do I know:
D400 will be FX format with a DX sensor inside.
5 fps at FX, 6,5 fps at DX format.
16 MP in FX, 6.9MP at DX format.
A new LCD, with 3,5" two fingered touch screen (wow)
Possible release will be May 2009
Extreme predictions : May have a GPS and wireless system
Expected price tag will be around 4300US$/Euro