I agree, Riku was a pretty anticlimatic final boss. I beat him relatively easily, and if you glide enough and have a lot of magic, you can go through the whole thing without getting hit once. Xion was a very hard boss, to me, especially in Halloween Town. That Ragnarok...
I'm not sure about his loyalties, either. Not much was learned about him, except that he view life as a game, basically.
Do you think it will start soon?