Looks like Carnival is already taking bookings for a cruise departing Miami May 1. Cleverly, they have planned "architecture tours, meetings with artists and musicians, discussions with local entrepreneurs, visits to coffee plantations and farming communities, and opportunities to try local rum and cigars" to fit within the current US restrictions.
Seems like a smart move on their part, since one of the biggest issues I hear about for tourism to Cuba is hotel space. A cruise ship would solve that and the tours allay peoples' fears of being on the wrong side of US policy. It's ridiculously expensive at $1800+ for a week, but people seem to be buying.