They are already experimenting with adding sails back to cruise ships, the potential cost savings should be enough to get the companies to change on their own.

I say this as an avid sailing but the downside of sails is that you cannot rely on them to get you where you need to go on an exact day, which is kind of the point for modern cruise ships. However if they can use them for the long haul passages then that at least will get away from the heavy oil that they tend to burn away from shore, although some still burn it close to shore even though they are not meant to.

I cannot see them getting away from having to use motive power of some description to drive props but electric drive does look promising for cruise ships, lots of ways to charge batteries for that.

The other problem with cruise ships is the local environmental impact of dropping that number of tourists at once on a single location, but cutting back mass tourism is a much trickier problem to deal with.