Um, no they won't. Nothing short of a hurricane-style storm will cancel a cruise. I don't think more than one or two have ever been canceled because of a bad crossing. At worst they'll take a circuitous route or wait a few hours to depart.
You don't think more than 1 or 2??? I'd take you @ 3+ if you're willing to bet. I've seen over 5 people post online that theirs cruise through DP was cancelled due to bad weather conditions.
I'm sure its very rare, though. And at times that you wouldn't want to risk it.