If that were the case then the movie would have a "dead end" with no possibility of sequel, unless of course you buy the expansion movie pack "Fallout 3 - Broken Steel"
But seriously, you would need to play the other two games to understand. The original Fallout set the stage of a sheltered Vault Dweller going out into the wasteland and becoming a hero that saved the vault, but could never return to his/her sheltered existence because the wastes have ultimately hardened and changed that person that his or her return would cause an irreversible stir in the once stable vault community. Fallout 3 borrows that concept and so much more from FO1 and 2. I do admit however, that it would be interesting to see post-apocalyptic DC on the big screen...
Like it was mentioned in a different post, it would almost be better to create an original story based in the Fallout universe, perhaps the plight of a different vault in a different region.