I think it's more complicated and open than that. In original Philip K. Dick's "Do Androids Dream Of Electric Sheep" Deckard passed the Voight-Kampff test without innuendos. Ridley Scott always wanted to make a noir movie with original Blade Runner, where the main protagonist ultimately hunting his own kind. Scott also said
in a 2014 interview that Deckard is a replicant. That's his vision.
Now, Harrison Ford's take on Deckard was different. He stated on some interviews that during Blade Runner's filming he and Scott had a struggle with Deckard being a replicant or not ; Ford thought the audience needed a "human representative on screen, somebody that they could have an emotional understanding of." He also said in a more recent interview than his opinion on the subject ultimately "didn't matter".
There's also the six different versions of original Blade Runner. While early ones cleary go in the "Deckard = human" direction, the latest version (where Scott had more control than the 1982 release, butchered by studio executives), the 2007 Final Cut, clearly implies that Deckard is a replicant.
I'm not even gonna summarize what the different writers have said because what I think matters is Blade Runner 2049 doesn't answer to the question ; during Deckard and Wallace confrontation, when Wallace wonders about Deckard being a replicant, Deckard answers "I know what's real".
What I think is Scott's vision regarding Deckard was always that Deckard is a replicant, he wanted it to be ambiguous, the studios hated the idea (hence the butchering) and even some of the crew didn't like it. So, who should have the last word ? The 1982 director, the studios, the writers, the actors, the 2049 director ? I know it's kind of shallow saying "it's up to the viewer to make up his opinion" but really think that's what Scott had in mind back in the day.[/URL]