I would say that you should enjoy your D3 to its fullest potential, and THEN make the decision to cry/scream/do pushups/swap to the D700 once Nikon ACTUALLY SHIPS IT TO STORES!
The D3 is the cream of the crop, and there is no reason to be upset about having one... but if you want to offload it to a broke up-and-coming photog, I'll message you my shipping address!
Heck, I just made the step up to the D2H (from a D40), a far inferior camera compared to the D3, and I couldn't be happier with the ergonomics, ease of use, and amazing auto focus system. I'd say you'd be best served by investing in better lenses, and enjoying the camera you've got by shooting at least 1000 shots per week!
Just my $0.02... for what its worth, -J
EDIT> I didn't realize that Nikon has unvailed the D700... SEXYTIME! Until it hits shelves, I'd still say enjoy the D3 and maybe get a backup D700 for it? I'll still take that D3 off your hands if you get tired of it!