David Jaffe emphasizes the importance of multiplayer in Twisted Metal and hints at DLC.
Jaffe states that the multiplayer is and always will be the main focus of the Twisted Metal series with single-player being more of a compliment to the game. Although he does go on to say that the single player and co-op modes of the new game are far more interesting and varied than any previous Twisted Metal game, but “it [single-player] is not Batman or GTA, and it was never designed to be.”
When asked about Mr. Twister and Slam, which were playable characters in past Twisted Metal games, he went on to say that those character will not be in the final rosters. He did however hint that they would possibly be the first DLC vehicle packs, but only after they see how well the game does, otherwise there is currently no planned DLC.
Be sure to read more about Twisted Metal maps.