Disney Answer: Yes and No
For the most part, yes, Disney Cruises are round trip. The Disney Fantasy and Disney Dream sail from Port Canaveral, Florida several times a week to Caribbean and Bahamian destinations and return back to Port Canaveral to start the process all over again. Disney’s other two ships, the Disney Magic and Disney Wonder sail to several different destinations around the globe from Alaska to Europe to the Caribbean and Bahamas. Once the ships arrive at their destinations, those cruises are round trip until the ship leaves for its next home port.
There are exceptions of course, as the ships are moving around (from Alaska and Europe back to Florida), the ships sail one-way Panama Canal or Transatlantic cruises. From time to time, Disney also does special one way cruises to destinations such as Hawaii or San Juan, Puerto Rico.
If you are sailing on the Wonder or Magic, double check your itinerary to make sure your cruise is round trip.