Not much. Frequent passengers are not as valuable as they are led to believe. Although it's more expensive to gain a new customer than to keep an existing one, it comes at a cost that needs to be balanced by the provider. Of course, with Covid, it will only make it harder to attract new clients short term as the overall opinion of cruising is pretty low in the general public's eye.
Upper mid-scale to luxury lines that have an even higher percentage of elite passengers than Carnival have this incorporated into their business model and attract a higher ADR and RevPAR. They know their onboard sales percentage will be lower than a cruise line that attracts a different clientele and thus have their lead in pricing adjusted accordingly (for the most part with some exceptions).
As a general rule, the more you cruise, the less likely you are to spend money in the cruise line's largest profit centers. You know how to price match your stateroom to get the best deal, you learn to utilize promotions to your advantage and stack onboard credits, you know how to research excursions on your own, formal night isn't as special so you aren't buying the pictures, you have the merchandise or only buy your select items for a collection, you avoid the land based shops the shopping specialist tries to send you to, you don't spend as much time in the spas as you did before, etc.