@MikeFrewer....D400....or whatever Nikon decides to make as a Pro DX. The above photo is only a cropped 10mm x 15mm size of the sensor on the D4 and was shot as an afterthought with the incorrect lens. So, noise is present.
I am waiting for the D400 and I think the delay is as I stated on the D400 thread, mainly due to the fact it will be the third "Pro" body Nikon has brought out this year and they do not want anyone canceling the D4/D800 orders to get a D400 instead. Most of my motorsports are shot at about 9 FPS, this allows plenty of editing out the garbage. When cars are moving by at rapidly changing speeds, above 120 mph, if one is using the long lens, i.e. 300mm or 400mm or even longer with the extenders, it is in my experience often times difficult to keep the car in the frame for all the exposures. I camera edit as many as 25% when I am shooting very close to the cars. Sometimes the angle of the shot fills the frame, and as they come closer, well, they spill out both ends...
But, again, the D400 will be the DX D4, IMO, and I am waiting for one myself.
And, the revised 80-400mm f/4.5-5.6 VR should be along sometime. Or grab a used VR in good condition. Look at this thread for an interesting comparison. http://nikonrumors.com/forum/topic.php?id=3549