Think about it. Bethesda has alot on it's plate between Elder Scrolls , Quake, Rage , and Fallout.
Do they have the man power to re-shape the Fallout universe or will they entrust that responsibility to some of the people who originally created it?
Bethesda has two branches: one is Bethesda Game Studios, the developer behind the Elder Scrolls series and Fallout 3; the other is Bethesda Softworks, which is the publishing arm of the company. Quake, Doom, and RAGE are all developed by id and published by Bethesda Softworks. Brink, Call of Cthulhu, Hunted, Rogue Warrior, WET, and the Elder Scrolls Travels series are also developed by studios other than BGS.
BGS is large enough to maintain staggered developement on two major titles at the same time: Fallout 3 completed almost all of it's pre-production while Oblivion was in developement and it appears that Skyrim was in pre-production while Fallout 3 was in developement. During the fall Todd even mentioned that they had a title other than Skyrim that was in pre-production - we don't know what it is but there are many people who expect it's Fallout 4.
When Bethesda initially licensed the IP the got the rights to make three games, and after purchasing the IP outright they remarked that it was a setting they really wanted to work with. I don't see them simply licensing it out to other companies . . . they may do this
in addition but there's no reason to believe they'll do this exclusively.
It appears this discussion has run its course so I'm going to close this now.