Thom Hogan sees two Nikon DSLRs and 2-3 lenses around mid-July
Check the Tom Hhogan website under June 2nd ("Rumble, Rumble") and you will find his speculation-prediction-rumors post saying that he expects two Nikon DSLRs and 2-3 lenses to come out around mid-July.
The Nikon D90 came out in the run-up to Photokina 2008, and by DSLR-years, it is overdue for a replacement, although historically Nikon is not as quick as some of the others (Sony, Canon) to launch newer releases.
If there is a second body, it would have to fit somewhere in-between the current line-up. Nikon's current DSLR line-up has a problem when compared to Canon - even though none of the actual dSLRs themselves have a problem. Canon has more of them - XS/1000D, XSi/450D, T1i/500D, T2i/550D, 50D and 7D, which Nikon only matches up with D3000, D5000, D90 and D300s. It is 6-on-4, and as hockey fans know, it is not a good matchup!