Proof on whether Deckard was a Replicant or not?

To be fair, he would have been hunted for disappearing with a fugitive either way. 

True, the "we" could mean Deckard and Rachel, but I kept wondering why Villeneuve would be unhappy by the inclusion of that line in the trailer unless it gives something away.

This is from ScreenRant's interview to give more context.  Villeneuve was talking about secrecy and wishing audiences could go into a movie knowing almost nothing about it.

DV - "...Because right now we see tons of images.  Two days ago, Joe Walker, my editor, saw the trailer and was watching like (does something non-verbal).  And I was like “It’s ok Joe, it’s ok, it’s ok".  Because there are things you work hard to try to keep secret, or create tension, or two characters try in a room to create surprise in the movie.  Then you look and the marketing department just shows it all.  For me, I don’t like it.  I wish one day I will have control.  I understand the importance of marketing.  I understand competition.  I understand the needs.  But I wish we would be able to sell movies without showing too much of it.  In a perfect world…"

SR - "The line, 'We were being hunted…'?"

DV - "Yeah, yeah, yeah.  I wish it was possible, but what can I say?"