The new Star Wars: The Last Jedi trailer hints that Luke or Rey will probably be Gray Jedi. The Gray Jedi believe in balance of the Force; whereas Jedi and Sith are on polar extremes between passion and detachment. The iconic symbol shown below from the trailer would seem to indicate so: If Luke or Rey end up as Gray Jedi, using philosophies of both sides of the Force, it could really mean the end of the Jedi, as suggested by the movie title. Or, at least the kind
