Rumors are flying high in the dpreview.com forums. One of the guys (Thom Hogan) there with connections into Nikon is claiming to know more about the specs of the upcoming Nikon D90 which are: 12MP, 4.5 fps, 3" LCD (but apparently not with 900k pixels), live view and equipped with GPS and last but not least a movie mode (there's also a microphone built in)! If he's holding us for fools, he is pretty good at it, because a movie mode would be absolutely welcomed on a DSLR. If the quality is significantly better than what the compacts offer this would give lots of possibilities regarding wideangle capture, which the camcorders usually don't do (they start at 35-40mm equivalent focal length).
The next rumor is about a new kit lens, an AF-S 18-105mm f/3.5-5.6 VR which will probably replace the AF-S 18-135mm. Nothing is known about new prime lenses featuring AF-S and/or VR or if other lenses will be updated.
Let's see if this holds true and what the price will be. In the end it could all just be a hoax. But it's very likely that there will be "something" introduced before or at Photokina 2008 in Cologne, Germany next month.
Update: A picture has surfaced showing the new D90. While it looks very realistic there is still no official announcement from Nikon. Note the microphone above the D90 logo.