As for how many movies Lucas "always planned", I am contesting the idea that he was actually talking about how many movie he was talking about doing, and instead suggest that he is talking about how much "story" he originaly came up with.
I believe that when Lucas says that the idea he had anything planned beyond episode 6 was a "media myth", he is talking about the fact that he tied up the whole story he had in mind for 9 films within 6. Instead of having the resolution of Vader and Luke thwarting the Emperor in the 9th episode, he pushed that up to the 6th episode, therefore the story has come full circle, and Lucas hasn't come up with anything beyond that resolution for the story.