Given the backlash felt within the community about the possibility of a voiced playable character, I'd like to offer my own insight based on previous Bethesda titles involving big actor names.
The voice in the trailer has all but been confirmed to be Troy Baker, not someone you recruit to do a couple of trite side-dialogue.
Similarly, Fallout 3 featured a star-studded name, Liam Neeson, who played the role of your father. It would be unlikely and impractical for a voiced PC due to the nature of communication in the game focusing on subtitles, and the fact that not a single Beth game up to this point has ever featured a voiced PC.
Therefore, I'd assume that Troy Baker's role in the game is more supplementary. Perhaps your father again. After all, it has not been confirmed that the man you see tending to the dog is your PC, it very well could simply be a place holder as of now.