Angel
For a good perspective of the way Nikon's DSLR lineup is affecting one pro who uses both the D3 and the D300, go to Thom Hogan's initial view on the D700 here:
D700 Announcement by Thom Hogan
Note he says: "for the time being, that's exactly what I'll do: shoot D700 main and D300 for pixel density." That would seem to fit your situation, and may fit mine eventually too!