I think that BBS will introduce us to the heartless; their origin. This is prolly the main reason why Maleficent is in BBS. This is what I think will happen: She will discover the heartless some way and learn about their power. She realizes that with the heartless' power she can control her world and others. But i dont think she is the only one who learns about the heartless. I think in this game will will see Zexion's, Xigbar's, Lexaeus', Xaldin's, and Vexen's true selves and how they and Xehanort experimented on the heartless. I think the ending (who ever has the FINAL ending to the game) will involve fighting heartless, and the take over of Radiant Garden and Kairi's arrival in Destiny Islands and Squall, Yuffie, Cid, Aerith, Cloud, and Tifa leave the world and Squall changing his name to Leon. The only thing I'm unsure about is Master Xehanort and his connection to the heartless and Xehanort. And i believe the new enemies are created, not born. They could be like the artificial heartless, and it could explain what happened to them (i think they were prolly destroyed by the heartless).