You'll get to fight Monstro the whale and even, well, [SPOILER] in the upcoming remake of Kingdom Hearts 2, which will be out December 2 for PS3.
Square Enix just released this new trailer to show off all the new stuff they've packaged into the HD collection, which they're calling "KINGDOM HEARTS HD 2.5 ReMIX." It includes the remixed versions of Kingdom Hearts 2 and Birth by Sleep, which were previously only available in Japan. It's also all remastered with fancy high-definition graphics.
Check out the trailer for a detailed breakdown of the new bosses, cut-scenes, and challenge modes they've added to this one. Also, keyblades. So many keyblades.