As for dystopian nr 1 (innate, shouldn't you call your topic 'possible dystopian futures'?), the atomic blast one; I think that nuclear armageddon is quite impossible, until at least some freak on drugs presses the red button. In my oppinion the 'fragile ballance' Deckard described, is not that fragile at all, because nuclear weapons are mainly used to frighten and threaten hostile countries than to blow things up.
I just hope, of course, that the 'cool heads' mentioned by Socrates will never fail.
As for the dystopian future which included humanity dying out thanks to neglecting breeding for the sake of computer games, I think, like innate, that this should be called utopian and considered as the only way of Heaven on Earth coming true.
About water contamination. I know quite a few things about water refinement, and am aware that there's nothing that nature wouldn't deal itrself, if we gave it time. (Maybe besides nuclear contamination....) So if Texaco or any other companies installed multimilion dollar ecological installations, stopped pollution and so on, we would have large amounts of drinking water anywhere.
But then again, it won't happen.
So, if I were to guess, I think technologically developped nations will continue to devastate Earth, until some LARGE and evident dying starts. And I don't mean Africa's population dying out of hunger, which is a fact - but is not connected to ecology that much, but I mean, for example, I don't know... maybe people in US starting to die because of lack of water.
This could open some eyes.
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Forgive my cosmic grammatics.