Not really, no. The GECK will refuse to load TES Construction Set files, and vica verca. I'm almost confident that it will not only be difficult, but also be illegal to port Fallout 3 content over.
Hmmmmm but thats not the same difference here - Obsidian used the GECK to build New Vegas, which was not the case with the jump from TES to Fallout3. NV has been described as a Shilvering-Isles-type size expansion to the Fallout3 game, and they used Many of the same resources as those in Fallout 3 (from the mag pics). It makes alot more sense that the GECK would work with the files. So Obsidian would have had to convert the existing Fallout3 models/meshes/textures to some other format for them not to be compatible with the GECK, and I don't see that happening in an 18-month window. Clearly the Fo3 resources had to be modified to make them work with NV - OR - they are not making as radical a change to the engine as many might suspect.
Wasnt New Vegas being done by a different company, something like that?
In that case, would we even expect to see a GECK version release that can edit it?
Considering they built NV with the GECK, I would think that if they Do release a CS with the tool - it would be the GECK. Respectfully, I'll hold out hope that we do get a GECK update, and that the GECK will still work with the original Fallout3 files. I don't expect to be able to run my mod or Fallout3 binaries in the New Vegas engine, but it wouldn't surprise me either if Obsidian keeps the same format for the ESMs as used in Fallout3, and simply added bells and whistles to their own version of the Binary to add effects.
I have hope!