As The Vault reports, Bethesda Softworks has recently registered Fallout as a trademark for "entertainment services in the nature of an on-going television program set in a post-nuclear apocalyptic world."
Interestingly, the registration took place on January 8, 2013. Erik Dellumes teased Fallout 3 fans on Twitter a day later. Make of it what you will.
Link: Bethesda registers Fallout trademark for a television program on The Vault