According to an anonymous, but fairly reliable source of mine, developers at Obsidian like Chris Avellone are not the only people who worked on the original Fallout games and are coming back for Fallout: New Vegas. Mark Morgan, who composed the Fallout soundtrack and Fallout 2 soundtrack (as well as the music for Planescape: Torment) is reportedly working on a project for Obsidian - and I highly doubt it's Alpha Protocol.
I, for one, hope that the rumor is true. And it's pretty plausible - after all, in this interview from a couple years back he said he was hoping for a job on Fallout 3. Stay tuned for first official New Vegas information in 3 weeks from now.