According to the team at the #1 Fallout wiki on the Internet - The Vault - it looks like Bethesda Game Studios is seeking experienced programmers to work on Fallout 4, the unannounced next iteration in the iconic Fallout franchise.
The official listing, posted on Zenimax Media's career page, says the studio is seeking 'experienced programmers to work on cutting-edge technology for an unannounced game on future-generation consoles.' While this could be for any game, it would definitely seem that Fallout 4 is in the works as Bethesda Game Studios typically develops The Elder Scrolls and Fallout franchises.
As 2011 saw the smash-hit Elder Scrolls V: Skyrim hit shelves, it only makes sense that the next game in the cycle would be a Fallout title.
Be sure to drop by The Vault for more speculation and discussion on this much-anticipated title as well as info on all of the previous games in Fallout's illustrious catalog.