He might have an insurance policy. After all, he had access to other data so if they lock him up, they risk problems bigger than they could ever imagine. He may have written a program that releases the information on a certain date. Or someone else has a backup and knows what to do with it.

Either that or he's no longer in Hong Kong, sort of like what McAfee did, tell everyone where he's at when he's really no longer there. So when Snowden tells the CIA their office is across the street, it's no more than a tactic to mislead the CIA.

Either that, or he hasn't thought this through at all and I find that hard to believe.