Doc's never coming back.
2 seconds sound clip from the Back to the Future Part III movie soundboard.
You can hear this line at 01:48:25.960 in the DVD version of the movie.
Quote context
[...]
- Yeah, you think I'm stupid enough to race that asshole?
- Jeez! I would have hit that Rolls-Royce.
- You're right. There's not much left.
- I'm sure gonna miss him, Jen.
(TRAIN CROSSING BELL CLANGING)
- Doc!
- Marty!
- Meet the family. Clara, you know.
- Ma'am!
[...]