If you are a U.S. citizen, you may travel to Puerto Rico and the U.S. Virgin Islands without a passport, since these islands are part of the United States. All other destinations require you to have a U.S. passport or a U.S. Passport Card to travel.
Passports were first required for cruise travel about 10 years ago. At the time, there was a rush by travelers to renew their passports or to get one for the first time.
Because passports are valid for 10 years, many will soon be expiring. That means there could be a rush and delays if many travelers want to renew their passports at the same time.
Even if you don't anticipate needing a passport soon, it would be wise to beat the crowd and renew your own passport now.