Wow, I never even considered that possibility. Has anyone read "Do andriods dream of electric sheep?" by Philip K Dick? For anyone who doesnt know, Bladerunner is based on that book but the film (dc version) is Ridley Scott's reworking of that story into a futuristic film noir (You dont get too many of them around!). Anyway, if memory serves, in that book there is a bladerunner that is himself a replicant and Deckard nails him. Deckard is not a replicant in the book but in light of the question and other answers, and with that snippet from the book in mind, I think RS probably meant for us to consider the fact that Deckard might be a replicant. Marvellous film and book too :-)