I went with the middle ground. First off, I certainly hope that we can extricate ourselves from our current sticky situation, and hope is worth something. Not much, but something. Second, even if worst comes to worst with the whole global warming thing and the ice caps melt and flood the planet, we'll lose people in droves, but there'll still be enough habitable land for us to fight over. And third, if there was a nuclear war tomorrow, humanity would still survive in pockets - our average life expectancies may drop to 36, and we may have our tech level blown back into the Dark Ages (or at least the nineteenth century), but there would still be people, and plenty of 'em. Bottom line, I don't see the human race going extinct any time soon.
Four Colditz salads and a Hermann Goering.