I'll look seriously at a D700 when reviews are available showing image quality. Higher image quality, especially at higher ISOs, has got to be a good reason for getting this body.
With a noisy D200, there are many times that I would like to use a higher ISO, but don't. The situations for this don't have to be really low light - I might just want a faster shutter speed and/or smaller aperture. I'll keep the D200 for when I want better reach.
I expect that the D700 will fall quite a bit from its launch price. I think that the D300 was launched at about £1300 & it is now retailing for about £100 more than the D200 was a year ago. So, I'll wait a little to get the new body.
Meanwhile, the reason for delaying lens choices (DX vs FX) seems to have gone. My next purchase could be the 24-70mm, which will work fine on my DX body for now, albeit that the zoom range is better suited to FX.