Interesting question. Although I think it might be grasping at straws. I think Lucas just used it as a plot device. It gives us a (cheap) explanation as to why a bunch of Jedi Masters could not sense a Sith Lord right under their noses. It also adds (supposedly) more meat to Anakin's story arc and makes his sacrifice and destruction of the Sith in ROTJ more final and meaningful., after all, it is the Tragedy of Darth Vader. Lucas didn't think he was ever gonna make the ST when he was making the PT, and now he has found himself written into another corner. (The other corner he wrote himself into concerns the villain. The Emperor was supposed to be the main villain, but again, when he was making ROTJ, he didn't think he was going to make the ST so he killed him off) More evidence to the fact it is a plot device Lucas just pulled out of his ass is the fact that there is no mention of it in the OT. My guess is that either one of two things will happen in the ST: It will be ignored and not addressed, or Anakin will appear as a force ghost and give a flat clumsy explanation, similar to how Obi-wan pointlessly appeared in ROTJ to retconn all that family stuff. As for the villain issue, I think Lucas will do the same thing he's always done: make it up as he goes along.