Not all sharks are live bearing, and not all give birth or lay only a few eggs at a time. Some can lay 100's or even 1000's but the end result is the same, only a handful make it to adulthood. Add to that, no one really knows the lifecycle of most shark species either so no one knows what their true population numbers are and they could be decimated or doing just fine.
I wouldn't really count on them being just fine though.