During Square Enix's Tokyo Game Show 2015 stage event, Kingdom Hearts HD 2.8 Final Chapter Prologue was revealed to be in development. The game includes a full-HD remaster of Kingdom Hearts 3D: Dream Drop Distance, a completely new HD theater cinematic called Kingdom Hearts χ Back Cover and a short brand new Kingdom Hearts playable episode called Kingdom Hearts 0.2 Birth By Sleep -A Fragmentary Passage-.
During June we got a new look at the game, thanks to an E3 trailer, but we didn't get many details on the game. Taking a look at the official game page (via NeoGaf) though tells us a bit more.
In the upper right-hand portion of the site's navigation bar you'll find a tab for "Special/DLC." The page is not yet active, but the tab suggests that there will be downloadable content for the game. What type of content we will be seeing has not been revealed. There is a chance that the tab is referring to downloadable wallpapers and the like, however, until Square Enix makes the tab live, we won't know for sure.
If it is DLC, hopefully it's just cosmetic.