Well, being that I'm a Christian, I personally believe that the world will end when none of us expect it, and when God essentially "sees fit" to call his children up to heaven.
*I don't ever put down on another religion, be sure of that. I'm not a Christian who bashes people who aren't Christians and crap like that. I don't try to impress my beliefs on others at all but I will talk with others if they ever wish to.