I would say probably not. I've never been able to get off the ship by 7:00am, and I wouldn't count on being able to do it. When the ship clears is up to Customs and Immigration, not
DCL, so they won't even be able to help with that.
I think they usually clear the ship between 7:30 and 8:00. If you were to be the first off at 7:30, find your luggage with a minimum of hassle, and get out of the terminal right away, you
might be able to make it. I just wouldn't count on it, as missing the flight would be a very real possibility, and that would put a damper on the last day of your vacation with the hassle of re-booking.
In addition, the ship is occaisionally late getting into port, which would definitely make you miss your flight.
DCL suggests that you allow for four hours between port and airport, which is probably a bit much. I personally wouldn't book a flight any earlier than 11:00am, and even that might be pushing it.