I faced a similar decision. I had a D700 and (at the time) D7000. Knowing that the D700 was discontinued, I chose to pick up a second body. I did so because the D700 is all the camera I will need to do what I want to do. Also, I didn't want the larger files of the subsequent models. But the biggest reason was that I felt more comfortable with the D700 than with any camera I've ever used.
If any of this seems familiar to you, go for it. But, as was mentioned above, if you don't need it or are just buying to be buying, you might reconsider.