Other episodes of the Heavy Rain Chronicles will serve as prequels to the main game. For example, the already-revealed taxidermist scene will explain why Madison Paige is an insomniac. Additional episodes will focus on the other characters in the game, with another revealing how Norman Jayden became addicted to drugs.
The taxidermist episode will be about an hour long, and it's likely all future episodes will be as well. Cage didn't go into details on when the episodes will be delivered or how they will be priced. Depending on the success of these episodes, Quantic Dream may want to pursue even more prequel stories, considering a sequel simply doesn't seem likely.
[Thanks Elena P.!]