I prefer Deckard's status as either a Replicant or a human to remain ambiguous. To me, the film asks the question, "What does it mean to be human?" or "What makes a human a human?" (The company motto is "More human than human" after all.) By creating the Replicants as a "slave race," mankind has lost a piece of its humanity.
This, of course, flies completely in the face of Dick's "Do Androids ...?", wherein the androids without a doubt embodied the absolute worst of humanity.
I could talk for days ... god I love this movie!