How about we quit fretting about what could be and deal with what is. Declining numbers on all fronts for infection and death. Increased natural immunity and herd immunity. Increased vaccination for those desiring to be vaccinated.
It should be fairly observable that we have reached a break even point. To strap additional stresses upon travelers does little to promote health and continues to degrade mental wellbeing. COVID more than likely isn't going away and we must, like all others before it, learn to live with it in the background.
We can bring up a hundred "what ifs". What if an unvaxed person brings back the virus... What if a vaxed person brings back the virus... What if a vaxed person leads to the death of an unvaxed person due to their unsanitary procedures... But none of that matters. It comes down to being an adult, making wise choices for yourself, and being responsible for said choices.
If we look at the science, it is interesting to find that the infectious distribution shows no difference between those that followed CDC recommendations (isolation, masks, etc.) and those that didn't.
For cruising, this means continued washing and healthy patterns without segmenting nor isolating cruisers due to opposing choices which both support healthy living.