I have had a D90 and currently have both the D700 and D7000. Firstly, I cannot agree with any comparison of the D7000 with a D700. They are fundamentally different in both technology and lens format. My advice would depend on what genre your photography fits into. If it's BIF, wildlife, sport etc, then the DX sensor is better in my opinion although I do use both DX and FX cameras occasionally. I say this as I use 35mm lenses and achieve x1.5 extra reach with the D7000. I use my D700 principally for landscape, portrait, weddings and architecture etc. The combination of a D700 with my 14-24mm f/2.8 lens is the wedding group shot camera/lens combination to have. As a wedding photographer I think you would really appreciate the FX sensor.
You have a dilema in so much that the D700 will possibly be replaced within 12 months, but that said it is a fantastic camera and I highly recommend it. I changed my D90 for a D7000 and as those on the forum know from my posts it was not a seamless transition by any means. I do find the D7000 as capable for my needs (and high ISO's are vital for BIF especially) in low light conditions.
The bottom line and my advice at present, if I were in your position, would be to buy the D700 and keep one D90. I always found the D90 an equally able camera for my use compared to even the D300 I had. I have got used to the D7000 and it is a very capable camera, if not well overpriced even now.
Your biggest decision in my view concern your existing lenses. If you have DX lenses only then it's going to be a poor move to a D700, or a very expensive one to buy 35mm lenses. Whereas, moving to the D7000 is not a problem of course.
The only thing I can say with certainty is that the D700 is a terrific camera. I can assure you the replacement will have to be some camera to make me change up. It certainly won't be because it has video!
A difficult decision only you can make, but I hope my experiences help in your decision making.