>A D400 shooting 8fps x 24 mpx would outgun the D4 in terms of >sheer bandwidth and I think that creates some serious >marketing challenges even after the technical bandwidth >challenges are overcome.
This has never stopped Nikon. The D7000 has a better sensor, more dynamic range, and a newer focusing system than my D3s. The D800 had a better sensor, faster FPS, better focusing, etc., than the D3x which was 2.5x it's price.
I would say it's a safe bet that if the D400 arrives it WILL be a 24Mp 7-8fps camera. If it falls below on either of those standards, then the D800 offers more MP, and the D7000/D600 will offer similar speed.