In the second teaser trailer, Luke says, “The Force is strong in my family. My father had it, I have it, my sister has it…you have that power, too.”
It didn’t appear in TFA, so maybe we’ll see it in VIII, and while it’s not definitive, it does imply a familial connection between Luke and Rey. (It’s clearly a new recording of Hamill’s voice, and my assumption is that it’s being spoken to Rey.)
It was kind of depressing to watch all the trailers again, because the trailers are excellent.
I thought it was confirmed in an interview with Abrams that the line was recorded solely for the purpose of the teaser. I possibly read it in Vanity Fair, I can’t remember. They recorded Hamill saying the dialogue again, then layered it over the original lines from ROTJ, giving it that echoey (I suppose, Force vision-like) quality.