Senior Producer Jason Bergman has said in an interview with Destructoid that they are working on FNV DLC.
He did not say what DLC is being made, but said they are more focused on "getting the game out of the door first".
The DLC will come out shortly after release.
Also, here's Destructiod's interview with Josh Sawyer
The interview also reveals that they are not doing anything at this year's London Expo.