Jared Leto has revealed that he is the only person who truly, definitively knows if Deckard is actually a replicant in Blade Runner 2049. In the belated sequel, Leto plays Niander Wallace, a serial industrialist who specializes in artificial food production, space colonization and, of course, replicant creation. His goal is to find the child of Deckard and Rachael in the hope of figuring out how to get replicants to pro-create, thus creating a near-infinite army of slaves.
In the movie's third act, Wallace kidnaps Deckard in an attempt to find out who he left his daughter with. A key part of the ensuing mental torture is playing with the popular fan idea that Deckard is himself a replicant; Wallace posits he was only created to fall in love with Rachael. The film ultimately doesn't provide an answer, maintaining the 35-year-old mystery, although it seems the villain at least knew the truth.
Speaking with Collider, Jared Leto discussed the long-standing question and said that at one point during production director Denis Villeneuve told the actor to come up with an answer in his own mind:
"Well there’s this scene where I look into his mind, right? I don’t know if it’s in the movie anymore. But Denis told me, I said, 'Denis, what do I see?' And it’s like a long pause, he walked away a few paces and he comes back and he says, 'This is your decision to make. You decide whether he is a replicant or not,' so in some way, I’m the one that has the secret now."
The scene Leto references appears to have been cut (the Oscar-winner famously never watches his films) but likely would have seen Wallace read Deckard's mind similar to how Ana watched K's memories earlier in the movie, in the process learning the truth of his origins (presumably by the presence or absence of implanted memories). As written, the scene presumably didn't have an answer - Villeneuve and all involved have been keen to keep up the ambiguity - but the notoriously method Leto clearly wanted to be sure in himself when playing the part. Not that the director allowed him to make that decision lightly.
While this means Leto has a firm, canon answer to the question, it doesn't help provide a solution to the mystery; even if Wallace knew for certain Deckard was a replicant, he'd play coy as part of the manipulation. And that's important as Blade Runner 2049 hinges on the question remaining unanswered to the audience - it's not where Deckard came from that's important, it's where he ends up.
As for what Leto's own answer is, he'll probably never tell.
- Blade Runner 2049 (2017) release date: Oct 06, 2017