"It's time for the Jedi to end"
This comment from Luke, coupled with a shot of his silhouette on Ahch-To, ties together the previous voiceover. All together, here is the core dialogue we hear in the trailer:
Luke: Breathe. Just breathe. Now, reach out. What do you see?
Rey: Light. Darkness. The balance.
Luke: It's so much bigger. I only know one truth. It's time for the Jedi to end.
It sounds like the events that led to the destruction of his academy have soured Luke on the sacredness of the Jedi order. Like his father, he eschewed the values Yoda tried to instill and forged his own path. Now, after studying the history of the Jedi order, he seems even more disenchanted. Is he training Rey to be a Jedi, or is he teaching her a more balanced, less extreme version of the Force?