Well, I meant that having Deckard as a human sorta provides hope for humanity; it implies that as shitty as their society is, there is still hope, there is still a chance that perhaps someday, atrocities like what we see with the Replicants will be ended. Having humans and Replicants as two distinct sides doesn't really bode well for that. It's mainly a symbolic thing to me.

But... your explanation seems to be entirely opposite from the point you're arguing. Surely if Deckard were a replicant, that would mean that the two 'sides' were far less clear, because there are 'good' replicants and 'bad' replicants (though this is a grossly oversimplified dichotomy, and one of the film's main themes is the ambiguity of morality). If Deckard were a human, there are two far more distinct 'sides' in the films. The 'good' humans, and the 'bad' replicants. Having Deckard and Rachael as replicants muddies the waters, and encourages us to think carefully about what is (in my opinion) the film's main message: that empathy is not exclusive to humans, and that a thinking, feeling replica of a human should be treated as no less 'human' than a 'real one'.

The film is trying to point out that there really is no difference between an artificial human with fake memories (such as Rachael), and a real one. Yes, you can detect the difference with a Voight-Kamff test, but without that, Rachael is technically inhuman. In every other way that we qualify someone as being 'human' (being conscious, being able to think, being able to feel emotions, being able to learn, etc.) she is human. So why should we treat these replicants as sub-human? Is it right to treat them as slaves (which, remember, is the reason why Batty and his gang are rebelling)?

I'd rather forget Prometheus tbqh. In my opinion, Alien > Blade Runner >>>>>>>>>>>>>>>>>>>>>>> Prometheus. God I can't believe I wasted money on that.

Ridley Scott's career recently has been attempt after attempt to desperately try and remember how to replicate the success of his past works. First it was Kingdom of Heaven and Robin Hood trying to be Gladiator, then it was Prometheus trying to be Alien, and now it seems we have Blade Runner 2 looming ominously in our rear-view mirrors...