As the new D3100, D5100 and D7000 sets the market the third generation for the nikon, it is already too late to replace the D300s by the fourth generation nikon D400 very soon. The delay is caused by the double disaster hit Japan in March 2011.
Going back to D400, here are what will you face (more or less)
D400 will be DX format as a legacy. (0.63 ratio)
8-9 fps (11-12 fps with the battery grip)
24.1 MP
Programmable U1 and U2 buttons as D7000 (not on dial)
A new LCD, 3" two fingered touch screen (wow)
1920x1080p AVC HD video
ISO 100-25.600 (Lo 1.0; ISO50 , Hi 2.0 ; ISO102.400)
2 CF card slots
Increased battery life for over 1000 shots
Possible announcement should be around September 2011, release March 2012
Extreme predictions : May have a GPS and/or wireless system onboard
Expected price tag will be around 2.600US$ USA.
