At some point, assumedly around the time of the OT DVD release, Lucas must have had some kind of revelation as to how the Star Wars Saga would continue beyond ROTJ and ultimately come to a different conclusion. We have always been told that this was the story of Anakin Skywalker, with the OT being about his redemption by his son, and the PT being his rise and fall. Once we got ROTJ, closure had come, or so we thought. Clearly ROTJ was supposed to be the end until a certain point in time where Lucas either thought of something else, or do you think this was always the plan? My opinion on this: I think ROTJ was supposed to be the end until Lucas began to put together the PT. I believe that during the writting process for the PT, Lucas developed a concept for an ST that would allow him to take the story into areas that earlier drafts of the OT had explored to some degree. Many things throughout the Star Wars Saga were alternate version of previous ideas that were re-imagined and molded to fit the scaled down final productions. In doing so, Lucas used Anakins insertion into ROTJ for the DVD release and the PT to set up situations that will come to light in the ST. On some what of a side note, I'm not sure where the sale to Disney fits into this, as I think Lucas was going to do an ST anyway, given when the above all happened. I think he just wanted someone else to bring it to life so he could get on with his.