So this is what I gathered would Luke Skywalker’s role will be in the films. From pure speculation, I have a feeling that Luke when he went to self-imposed exile was gathering information on Jedi and possibly even Sith teachings (And if they want can go beyond those two main orders like the EU.) Combined with his potential he becomes the most powerful being in the Galaxy. The title is called “The Force Awakens." I have a feeling that Luke after spending decades of studying finally reached Oneness or Enlightenment through the Force, however at the cost of great power he mostly loses his humanity and social mind, no longer viewing the world like we do. Because of so many years of self-imposed exile combined with knowledge and power that many won’t grasp, he becomes an insane old Wizard like Joruus C’Baoth, who walks a fine line between the Light and Dark. He even uses Darkside powers like Force Lightning and any given moment could fall to the Dark-side. The villain could be someone who sees Luke as a Potential Super-weapon of sorts and hopes to turn him to his or her side.