Broken Steel

Broken Steel will be the third Fallout 3 downloadable content pack, to be released in March 2009 for Xbox 360 and Games for Windows Live.

In this DLC pack, you will join the ranks of the Brotherhood of Steel and rid the Capital Wasteland of the Enclave remnants once and for all. Continues the adventure past the main quest.

As of yet, there is no news of a PS3 release.

Spoilers and Character Generation Controversy
Given only one possible Fallout 3 ending permits the player character to survive, it seems likely that a new or heavily modified character will be required to play, unless the assumption is made that the player chose the "cowardly" path and escaped (which one might assume would not put him or her on good terms with the Brotherhood of Steel). The radiation levels appear to be so high in Take it Back! that it seems unlikely the character could even proceed as a ghoul In the final movie, it appears that you are reduced to a goo pile. However, when contrasted against the "cowardly" ending, Sentinel Lyons is not likewise reduced, and the goo pile present in the final video may simply be the result of the quickest way to code an ending without having to take into account the innumerable facial and constructural variations within characters.

There is a possibility, however, that followers that are immune to radiation will no longer refuse (because now the story goes further), and no-one will perish.

NOTE: I also believe that it is possible that the Vault Dweller survived as a Super Mutant, or atleast something in between a human and a super-mutant.