I think it's pretty safe to say that the GoL will be the ones that people actually suspect which are Sora, Riku, Kairi, Mickey, Ven, Aqua, Lea. I don't think it even crossed their minds to introduce even more characters. There's already too many as it is. Some of these characters you can't even really talk about. Xehanort was a misguided person but he's basically bad. Terra is like Riku. Kairi is a girl. Xion is someone who nobody remembers but she was pretty into sitting around eating ice cream and contemplating her own existence. There's no way they're going to be able to flesh out the personalities of all the ones I mentioned and there's a ton more that are even worse. The writers don't need any more characters to juggle and neither do we.