BioWare announced today via its official Blog that it will release the "Extended Cut" DLC next week. The DLC was in response to a firestorm online about how the things players do within the game didn't have a significant impact on the ending of the game. The DLC will be released on June 26 in the U.S and Europe for Xbox 360 and PC. While U.S. customers will be able to get the PS3 DLC on June 26, European players will have to wait until July 4.
The DLC will weigh in at around 1.9GB and promises to flesh out the endgame with additional cut scenes. The DLC doesn't actually change the ending but, according to BioWare, provides more answers and closure based on the way you have played the game.
You can find out more at BioWare.