YODA: Luke, when gone am I, the last of the Jedi will you be. Pass on what you have learned!
Presumably, this will tell the story of the rebirth of the Jedi order, of Luke passing on his wisdom to the next generation. This would fit the thematic elements of each previous trilogy, as well, and moreso if Luke were to die in the first film, in a lightsaber combat. Hammil could always reprise the role in later films as a Force Ghost. I imagine the film will not lack for Jedi.