In a recent interview with David Cage, founder of Quantic Dream, Cage revealed they are in talks with Sony to continue the storyline of the four main characters in Heavy Rain. He believes that players will get attached to the four main characters in the story, therefore sequels, prequels, or even both may be feasible as downloadable content.
Although I haven't even played the game yet, this news excites me..... In interesting ways.
...I must go now