This is one of the things to think about when you put your gear together.
If you are diving in warm water, with a thin exposure suit, and are properly weighted, you are at most 10 lbs negative at the beginning of the dive (weight of gas in an HP130). Most people can swim up 10 lbs, and you drop your weights AT THE SURFACE to remain buoyant.
If you are diving in colder water with thick exposure protection, you can add the loss of quite a bit of buoyancy from your neoprene to that 10 lbs. People I know looked at the loss of buoyancy from a 7 mil wetsuit and determined it to be about 20 lbs at 100 feet -- so now you're 30 pounds negative, and not many of us can swim that up. But, if you drop weights at that point, you absolutely will not be able to control your ascent once your suit begins to reexpand. So it's a good idea to carry some kind of redundant buoyancy -- or even better, not to dive deep in cold water in a wetsuit!
It is important to remember that, if your BC has a hole in it that's big enough to cause problems, there is still probably some orientation you can get in that makes that hole the lowest point of the BC, and the rest will hold air. (If the hole's in the left side, dive right side high, for example.) Worse than a hole is something like having the corrugated hose fail at the elbow, which is one of the reasons I don't like pull dumps.
This is a good question to ask and think about -- good on you for asking it.