George worked much the same way. He didn’t have the sister thing worked out yet when Yoda spoke of another in Empire. Did Irvin Kershner have to know if Vader really was Luke’s father or not to make that scene work?
I think someone at Lucasfilm will be guiding things. People are not just going to make up whatever they want.
That is true, but also remember that Star Wars was intended to be a stand alone film. A big difference here is this was known to be a trilogy from the get go. So the possibility that they put a bunch of mysteries in the first act that they don’t have any clue what the answers to them are and are then are handing it off to someone else is concerning. I am hoping that is not the case and they have something fleshed out.