When Luke Skywalker says it's time for the Jedi to end. I think he means the Jedi order as we've known it, servicing only the light side of the force. What if he means it's time to embrace the dark side as a way of seeking balance to the force, as Mace Windu did, which is explained in this video here. https://youtu.be/QWj21lPBY5M?t=3m43s