We think Visceral's missing out on a great chance to kill two birds with one stone -- why not make Purgatorio and Paradiso DLC packs for Inferno? For instance, a few months after the game comes out, release a patch that makes the game's load times last for 49 days. Boom. Purgatorio in the bag.
Update: As awesome as that sounds, it's more likely he was talking about the "Dark Forest" prequel DLC that will come bundled with the Limited Edition version of the game on PS3. We're still going to hold out hope, though!