Final Fantasy XIII producer Yoshinori Kitase has said that Square Enix are "exploring" the option of releasing possible DLC for the game on the PSN and Xbox Live with new items, areas or enemies, although nothing is set in stone yet.
If there was to be DLC for the game, it wouldn't tie into the story.
Anything story related will stay on the disc(s).
"We are exploring the option of downloadable content, perhaps adding new areas, items or enemies, but these would not be expansions to the story, only the gameplay. The entire story of FF13 will be on the disc," according to Kitase.
This would mark a major u-turn after the publisher stated there would be no DLC for the game at all a while back.
More over at RPGSite.