On January 8, 2013, Bethesda Softworks registered a Fallout trademark for “Entertainment services in the nature of an on-going television program set in a post-nuclear apocalyptic world.”
Interestingly, a day later, Erik Dellums tweeted that there may be more Three Dog coming. The furor that erupted in the Fallout fan channels was noticed by several crowd-sourcing news sites, including Reddit.
With the almost viral success of the fan-made Nuka Break web series, you would think they would have jumped on this right away. While this filing is not a guarantee of a Fallout TV series, it does show that they are thinking about it and protecting the future of the Fallout Universe.