It can happen again, if the cruiselines would market it better. There are certainly enough customers to warrant a non-smoking ship, yet the Paradise didn't change the intinerary enough. Who wants to go on their one vacation every year to the same ports as last year, and the year before, etc.
Also, they could market it to multiple groups of people who can't stand smoke. Such as, the AMA, Nursing Associates, Lung cancer survivors network, etc.
Never say never.