IDunno - the D5000, in my book, is not really a serious camera for someone wanting to move into the full realm of DSLR photography. I don't mean to diss the camera, it's actually a great little camera, but its build quality, feel, etc., are not on the level of a D90 or D300.
Nikon does have a problem in that the D5000 is so good, and so close in price to the D90, that the two camera's are somewhat competing against each other. I think most in this forum would clearly suggest anyone pay the $100-150 extra for the D90. A replacement for the D90 will have the same problem. I tend to agree with Niko that the new camera will not truly be a replacement (I know that's not quite what Niko said), but will be clearly slotted above the D5000 as a D7000 or such.
I stick by my guess that the new camera, after intitial price gouging, will retail on the street real close to $1000.