The rule of thumb for return flights is not to schedule anything before midday. Part of what time you leave on your final morning will depend on whether you're on main or late seating for dinner, as main seating eats breakfast first and can then leave the ship.
Usually we have a rental car and we're usually on the road pretty quickly after clearing customs and getting our cases. I don't remember what time we got back to Disney after our cruise on the Dream, but we had the early breakfast, and I'm going to guess we left the ship somewhere around 8am.
