Dengeki Online has an article on Dissidia 012[duodecim]: Final Fantasy this week, which mentions downloadable content plans. The magazine says players will be able to get costumes and music from the Final Fantasy series as DLC.
Costumes are hardly surprising, especially since PSP games like The 3rd Birthday, Kingdom Hearts: Birth by Sleep Final Mix, and Final Fantasy IV: Complete Collection come with costume codes for the PlayStation Store. First run copies of Dissidia 012[duodecim]: Final Fantasy in Japan also include code for an extra Tifa outfit (pictured).
Details about pricing for extra items have not been posted.