There were some rumors going on about Final Fantasy XIII getting downloadable content, but a few days ago Square Enix has stated that they currently don't have any plans for DLC.
In an interview with producer Yoshinori Kitase and director Motomu Toriyama by PlayStation.Blog.US said the following:
"Regarding the DLC content, we feel that the final product is 100% enjoyable…it’s the complete package. So we’re not planning any DLC at this time. In regard to the rumored cut content, we feel it was taken out of context. There are a lot of ideas that are brought to the table, and then the team takes the best ideas out of those, and the final product is polished that way. There was content that were “ideas” that didn’t make the final content, but the team isn’t looking to release that as downloadable content."
If the company decides in the future to release DLC, we will let you know.
Source: PlayStation.Blog.Europe