I think it's pretty clear that considering how this day ended, we'll see another installment of '24' some day. They're not going to let Jack rot in some Russian prison any more than they would have let him rot in a Chinese prison.
I'm betting FOX feels the ratings were strong enough to commission another summer series along this same format. They weren't great, but they didn't suck either. FWIW, I was surprised they weren't higher. There's a built-in fan base that will guarantee a certain Nielsen number.