Kingdom Hearts 2.8 will contain a HD remaster of Dream Drop Distance, along with scenes from Unchained X called Back Cover, set to tell the tale of the Foretellers and revealing new parts of the series' history. The final part of the collection is Birth by Sleep 0.2 - A Fragmentary Passage, which is a completely new part of the story taking place after the events of the original Birth by Sleep, told from the perspective of Aqua. Yeah... did you follow that?
The PS4 exclusive RPG is expected to launch in December, and will connect the dots between all the KH games and the eventual release of Kingdom Hearts 3, expected out in 2017.
Trailer and news via IGN.