10 Fascinating Theories About Star Wars: The Last Jedi
3. Luke Is Dismantling The Jedi
Luke's absence from the galaxy is partly explained by his desire to find 'the last Jedi temple'. Snoke's fear that the 'New Jedi' will rise if Skywalker is found suggests Luke intends to refound the Jedi order after making a hash of it with Kylo Ren and his knights. This theory suggests the opposite.
Luke has seen what happens when Jedi go bad, both with Vader and Ren, and has felt the Dark Side calling him in turn. He knows the dangers the Jedi pose, especially with none of the old Jedi masters, of Yoda or Obi-Wan's vintage, around to lead them.
This theory has Luke seeking out the last vestiges not to recreate the order, but to destroy it forever and prevent the Jedi from ever returning. The events of The Force Awakens could be a part of this, with Luke only reappearing after Kylo Ren, the greatest moral threat to a new Jedi Order, is presumed dead.
It's also the most direct fit for his mysterious line in the trailer: "It's time for the Jedi to end."