How's this for an idea? (to be taken with a grain of salt).
Keep the D80.
Take your $7k, and buy a 70-200 2.8, 24-70 2.8 and a 14-24 and a TC-20III. Keep the 28-105 as a walkaround / travel lens.
Wait a year, save some money, and buy whatever replaces the D700.
You will then have the "perfect" kit, and be able to take plenty of fine shots in the meantime with that glass.