Ridley Scott is loving his prequel/sequels recently. Blade Runner 2 is his latest project and he has confirmed that Deckard is indeed a replicant. (something that was hinted upon in the theatrical release of Blade Runner and less subtly hinted at in the Directors-cut)
But if Deckard is a replicant then how has he passed his 4 year life span? And if Harrison Ford is playing him over 30 years later then... how has he aged?
Sometimes I think its better just to leave the originals alone, Blade Runner is a classic! But Hollywood obviously disagree's as does Harrison Ford who can't seem to say no to sequels, appearing in the forth Indiana Jones film and in the soon to be released Star Wars films.
"But something doesn’t add up. Replicants were supposed to have a built in lifespan of 4 years, but Harrison Ford is reprising his role as Deckard the in the upcoming sequel. So…how does that work? “I’m not going to tell you,” Scott replied to Yahoo when asked. “You’ll have to see the story. It’ll all make sense.” Deckard will return in the next Blade Runner, before passing the torch over to a new lead character, played by Ryan Gosling. The film will definitely need to explain how a replicant like Deckard has survived so long, considering the timing that Scott has in mind." Blade Runner 2 is expected to begin production in 2016.
http://comicbook.com/2015/09/29/blade-runner-sequel-will-explain-how-deckard-is-a-replicant/