D7000 or Nikon 300mmF4

Better glass will make a bigger difference nearly every time. D7000 is a good step up from the D80 (resolution and dynamic range especially), but great glass = great images, even from "outdated" bodies. My vote is for the 300 f4 Besides, the lens will still be great even when the D7000 is way behind future technology...
--
K.B.