You people are making a big drama out of nothing,
I have managed cruise ships for over 30 years.
I have worked on nearly 1400 cruises.
The majority of those 1400 cruises were overbooked.
Nobody on any of those 1400 cruises was ever bumped.
The cruise lines always sweetens the deal until enough people are quite happy to take them up on the offer.
If you feel the need to worry about details of your cruise, this idea should be at the bottom of your list.
You can only hope that your next cruise is overbooked and you get an offer that you cannot refuse.