What if Vader didn't block Luke's strike on Sidious

   I know, double Star wars.But I <3 Star wars. To get to the point, in #6, Sidious says his famous line "Take your weapon, strike me down! And you journey to the dark side will be complete." This is scary because Luke actually tries! So what if Luke DID kill him.

                         Simple way
 With the Emperor dead, its Vader and Luke 1 on 1. We see Luke nearly kills Vader. Then he doesn't and says "I am a jedi, like my father before me." (Ya your father who killed jedis as kids). Vader sees his son and they rule the galaxy together. Or Luke kills Vader as well.
                      Most likely way 
  We see that through out the movies Luke turns dark. Killing Jaba's gards with force choke, entering Jaba's palace all black like sith, using rage to kill Vader like sith, and trying to kill Sidious. My prediction is... Sidious was right. Luke kills him and joins the dark side with Vader (either way, Luke and Vader team up. Was Sidious in the way of the father, son galaxy rulers?). This is more likely for even George Lucas to do because he says that the trilogies "rhyme". Example: Anakin never knew his parents on a hot planet, same with Luke, same with Rey. This would complete this "rhyme" making Luke's and Anakin's stories even more similar (maybe too similar).

             A funny note
 Imagine ghost Anakin meeting the ghost kids he killed. That would be so weird. They'd be like "YOU KILLED US AS CHILDREN!"