This very thread had people who felt it was better to use cash so they wouldn't lose anything if they cancelled. That tells me that there are probably a lot of people who feel they may not make the cruise. Thus, there's probably a pretty good chance your waitlist will come through.
The last cruise was much shorter notice, so a lot of people pretty much knew already if they would be able to make it or not. In some ways, I think this shows that it may actually be better to give less notice for these special cruises.