when it come to the ending i take all the info in KH, KHCM, and KH2 and i have come up with 1 conclusion KH3 will be a keyblade war in the realm of darkness just as riku and sora said the light realm is safe so the darkness needs to faught for so i think that the letter recieved at the very end (after the credits) states that there is a problem in the realm of darness (keyblade war) and the king, donal, and goof are going there and request that sora and riku join them i think that in KH3 like at the end of KH2 you will be able to let riku be in your group thoughout the game anf at some times play as him and as and obveous fact it will be on PS3.