We did the theater experience of "Blade Runner 2049" recently, so with that fresh in my mind we watched Blade Runner (2007 "Final Cut" based on 1982 theatrical release, taking place in 2019). (Also 50 First Dates, and The Duchess.)
Prior to BR2049's release, Scott declared it would definitively answer the fan theory question: was Deckard a replicant? In Philip K. Dick's source novel, "Do Androids Dream of Electric Sheep?" (1968), Deckard questions his humanity but the Voigt-Kampff test indicates he's human, or at least possessed of fully human empathy. The original 1982 theatrical release doesn't muddy those waters either. But in every version, at the end Deckard's handler Gaff leaves him an origami unicorn. In the theatrical release it merely shows that Gaff had been to Deckard's apartment and presumably knew Rachael was there. Gaff's 3 origamis are symbolic - a chicken when Deckard tries to beg off the assignment in the beginning, a man with a vulgar erection to indicate he's aware of Deckard's attraction to Rachael, and the unicorn perhaps to say he thinks Deckard is chasing a foolish fantasy by bonding with Rachael.
The 1992 so-called "Director's Cut" (which Scott had no control over) adds a scene where Deckard dreams of a unicorn, which changes the implications of Gaff's unicorn origami to imply Gaff knows Deckard's inner thoughts in unnatural detail, paralleling how Deckard was able to recite Rachael's childhood memories because they were "stock". Or to put it bluntly, Deckard is a replicant, a detail Scott himself confirmed in a Digital Spy interview. Incidentally, Harrison Ford long maintained his character Deckard was human, not a replicant. When it comes down to it, I suppose the director's vision must trump the actor's, though.
Except the camera didn't focus or linger on the origamis enough for me to realize their symbolism on viewing - only that they implied SOMETHING in the end. Not knowing that detail, it merely seemed a redundant comment after Gaff's spoken delivery - "too bad she won't live, but then again, who does?"
Scott hyped BR 2049 saying it would definitively answer the question of whether Deckard was a replicant. The late models of 2019 were built to die after 4 years, so obviously he wasn't one of those, but he was also advanced enough to question his own humanity, while Rachael was a late experiment in that she didn't know she was a replicant until Deckard revealed it. Deckard was also an investigator - it would be exceedingly difficult to keep him unaware of his own synthetic origin and contraband status.
Harrison Ford was a co-screenwriter of 2049, and in an interview he stated 2049 "resolved" the question of Deckard's origin. I can only assume his resolution with Scott was that the question should remain teased but unanswered.
I also learned Ridley Scott's Blade Runner movies are part of the Aliens universe. This has also been a fan theory for a while, apparently intentionally teased by Ridley Scott and kept simmering in the same way to keep audiences pondering and talking and waiting for the next unfolding. One of the big hints is a fictional 2023 TED Talk by Aliens universe robotics magnate Peter Weyland, whose reference to an unnamed former cohort or partner almost unavoidably suggests Eldon Tyrell. The Aliens fansite wiki treats the connection as cut-and-dried, and provides this chronology to tie them all together.