The D90 has come down in price on the slightly used market. Check over Craig's list in your area and you will find it from $650 to $1000 (with kit). I own a D90 and love the thing for back-up and everyday use. The D300 (non-S) is around $1000 on the market as well and the sensor and pixels are the same as the D90. If you are newer to the Nikon world the D90 is very nice with the "auto" modes when you want to get the shot now without thinking too much. If they release a new D90 this year I would be surprised considering the D700 is looking for the revamp and maybe another full frame.
My only complaint with my D90 is the white balance is sometimes off, I always shoot RAW anyway so that is easily fixed post with a click. The kit lens 18-105mm sometimes loses connection with the camera causing it to Err-- and you will have to re-seat it. I have never had any problems with other lenses.
I just don't see Nikon increasing the mega-pixel count anytime soon for one reason there is no point to increase it. Better ISO noise reduction is where they have been heading with all the cameras. Full frame will still be in the $2K range from the next few years maybe even longer.
The D90 all in all is a awesome purchase regardless. It will last for years and you can always use it as a great back-up as time passes.