I got a pretty cheap flight by flying on 12/18 & 12/25. I just checked and the return flight on 12/25 looks 90+ % empty (according to available seats on delta.com). I wonder how likely it is that this flight will be canceled.
I suppose I should look into what Delta's policy is when canceling flights. I'd imagine (hope) that they would pay for overnight lodging if the next available flight isn't until the next day? Hey, being forced to spend another day in Aruba ain't that bad
http://www.delta.com/legal/delta_customer_commitment/index.jsp "Providing meal allowances and hotel accommodations at Delta contracted facilities, based on availability, if you are inconvenienced overnight while away from your home or destination due to a delay or cancellation within Delta's control. If accommodations are unavailable, we will compensate you with a transportation credit commensurate in value with the contracted hotel rate.
Contacting you about cancellations when the event is known at least two hours before departure, averting a frustrating trip to the airport. "
If you flight is cancelled, it may be difficult for them to put you up in their contracted hotel, since on the 25th most, if not all resorts will probably be sold out. The bigger question though is obviously no one wants to fly on the holiday so those departing the island before the New Year will be doing so on the 26, 27 & 28th. Those passengers already ticketed on those flights will have priority for seating over you. You will be flying standby. It will be up to Delta to "squeeze you in" on one of those flights or on another airline (which will most likely have the same the capacity for passengers).
Given that the flights on the dates after yours are probably close to capacity, if I had to guess, would say Delta would not cancel the flight.
If you are worried about the flight being cancelled I would see if there are seats after the 25th to get an idea of you chances. Also try to consider an alternative airport destination in the US.
Why do I say all this? My In-laws were stranded in St. Martin one year due to a snowstorm in the northeast. Their flight out of SMX was cancelled and due to having to fly stand-by (again the passengers already ticketed on succeeding days are accommodated first) they were unable to get a seat on a plane until 5 days later. By changing their airport destination in the US (and on their own dime paying to rent a car and drive to their own home from there) they were able to get seats on a flight out of SMX 3 days later.
It looks like both of the flights down to Aruba is pretty full and they would have to cancel one of those flights in order to cancel the return. They have to get the aircraft back to Atlanta in order to get it back into the system, even if they aren't going to make anything off of the return trip itself.