In response to the original question, Frisky, I think it's impossible to say what might happen to 'most atheists' given that
a) the existence of astral planes is entirely speculative so there seems to be no real way to accurately guess how they might be apportioned, and
b) as people have been trying to suggest in this thread, 'most atheists' is entirely subjective. You know only a few atheists, and your opinion is that they're mostly 'negative and condescending', but I know a great many atheists and they're just regular people, perfectly nice.
My question in return to you is: What does it matter where they go?
It seems from the original question that you're interested in the idea that atheists should somehow be punished for their lack of belief. What would it mean if they weren't?