Here you will see how episode 3.5 would be like if George Lucas made one.
This is Darth Vaders secret aprentice that know one Knows about not even Darth Sidious.
His mission is to wipe out the rest of the jedi secretly. Kind of like an assassian.
Know if there will be an episode 3,5 there should be a episode 7 because after darth vader dies his secret apprentice is still left for luke to kill.
there is also going to be a game and a book that is coming out in April.