I wouldn't worry, we will cruise, we may not be cruising to the same places if we have a hurricane or tropical storm, but cruises go on.... they just divert...
I.E. in Nov 2001, instead if
RCCL's private Island, we went to freeport...
I have antcipated possible 'waves' due to 'bad weather' and gotten a package of Bonine (it doesn't make you sleeply like Draminine)
On our first cruise, the first day (same iternary, except we went to key west instead of sea day) I got 'sick' took dramine, was sleeply, and missed all the 'fun'... patches don't work either, a friend tried them... Bonine is great, and less than 3 dollars at wal-mart....
I got sick in Alaska too, and then in 02, Oct, we went to Bermuda, while Hurricane Kyle was 'circling' no rain except last day there, and other than 20 ft waves 'coming' in to Bermuda, we were ok (I had anticipated this, and me and mom got Bonine, started taking it two days before sailing, took entire time, and was ok... lots of people who had patches or nothing got VERY sick the last day coming into Bermuda...)
I always say, sea sickness is NOT determined by if you can ride in a boat on a lake, it's the body of water, how long your on it, and weather that determine that...
My advice... make the 'small' investment, get the Bonine, take in the day we leave (a few hours before we sail) and see how you are
(for all the new ones) The Atlantic CAN be a bit rough (especially to Honeymooners, the last thing you want is to get sick....

)
You should be ok the rest of the days, but on the last 'sea' day, you may again want to take one as that is when you are 'again' likely to get sick....
Check the weather, if Tropical storms and/or Hurricanes are in the vancitity, no matter how far, get more Bonine enough to take everyday...
20 ft waves are pretty bad, but if you got the medicine, you'll be fine (other than walking like your drunk, you won't feel it...)
sea sick stays untill you take medicine (a green apple helps too, a crew memeber told me this once), you throw up, and won't feel better, so don't count on that... like I said, Bonine WON'T make you sleeply, so you won't 'miss' anything...
Hope that helps...
any other questions, feel free to e-mail or pm me.
Meg