Instead of expanding the story or adding additional content, Ken Levine's goal with DLC for Bioshock
is to increase the replayability factor
. 1up reports: "'Diablo II, to me, was a great model for an expansion, because it enhanced the original game, but also extended the game, too. I'm not a really big fan of expanding things just by linearly adding to the experience, adding a new campaign, as much as I am of enhancing the original experience and adding replayability to that experience,' said Levine in a post-release interview in the latest issue of Games for Windows Magazine. 'I think that certainly BioShock's combat experience is great, but it could be broader. I'm a little more confused as far as how to expand the narrative experience.'"
He goes on to suggest some plasmids, cut during development, might see their way back into the game. Otherwise, not a lot of detail available on what 'adding replayability' might mean.