As I recall, he never intended to wrap up all the plots. Not so much to leave room for outrigger novels, but because he did not want to. Just as in life nothing ever is eevr completely wrapped up, he did not want to wrap this either.

RJ wanted intended to write a follow-up trilogy about Matt and Tuon but other than that I am not aware of any of his other plans. The open-ended intention was not a money grab for writing more novels, he had many other novels he wanted to write (somethign liek 30 years worth if I remmeber corectly, it is in his blog), but the nature of the wheel: nothing ever begins, and nothing ever ends...