I think that Brian is spot on. Look at the features and construction and what the pre-release users are already saying, not the model number relative to other model numbers and you will come to the conclusion that Nikon believes that the D7000 should be an improvement over the D90.

I think Nikon is in uncharted territory in terms of model numbers relative to their long history. The fact that they did not have a complete model number scheme outlined to last them 20 years into the future when they first released their first D-SLR is no reason to disqualify the D7000 based on its model number alone.