Cruise lines publish their rates over a year in advance. If you book early and inflation rates go up. Your price for the cruise is pretty much guaranteed. The dirty little secret is if the cost of fuel gets inflated. They can add a fuel surcharge to the cost of your ticket to help them reduce the amount of profit loss.
So in my opinion book early, especially if you feel inflation is going to be an issue this year. Then the only price increase you'll see, maybe a small fuel surcharge.