If you only have a DSLR and 85mm prime, you would probably appreciate having a zoom lens that covers wide to short tele. Some candidates:
1) 18-55 VR f/3.5-5.6 DX
2) Tamron 17-50 f/2.8
3) 17-55 f/2.8 DX
4) 18-70 f/3.5-4.5 DX
5) 18-105 VR f/3.5-5.6 DX
personal preference of course
Whether to get a new camera body or not, is entirely up to you and your budget
i would suggest u to get d700.
I was using d90 as well with lenses like 10-20mm, 35 1.8mm and 18-135mm. But decided to sell all those only to upgrade cam body to D700
U would feel a big different in term of color, sharpness and body is heavier.