Well the D600 is a $2000 body, and the only way you can outfit it with glass is with FX lenses which tend to be pretty expensive. I have a D600 and it makes a very good second camera for FX, or a light body for those situations. My D600 though has been converted to IR and its a top of the line IR body.
The typical D7000 user is going to be using DX glass rather than the pro lenses used by many of the D600 users.
I fully expect to see a top of the line DX body - something well beyond the D7100.