Here is my theory on the ending. In the film the ship arrives in New York and repairs are immediately underway as we hear drilling sounds on the deck and we see a crane lifting up part of a mast on the forward deck. Many flags of celebration are waving above the ship and there is a spectator's platform adjacent to the ship with many people watching. My guess is, the Titanic is inspected for damage and parts of her hull and decking are replaced. The enormous amount of cargo and mail that is still sealed in bags in the cargo hold is removed and the media make a novelty out of reading some of the letters that are still waiting to be posted to people in America. The media and special VIPS are given a guided tour inside the wreck while repairs are still underway and some decks are off limits. Furniture is removed and possibly restored or auctioned off, and personal belongings from the passengers and crew are returned to their relatives.
About 2 years later the ship is ready for paying customers and tour groups to explore under strict supervision. As the years go by the ship is furnished with reproduction furniture and lighting and the guided tour rules become more relaxed. About 5 years later the ship is bought and turned into a hotel. About 30 years later the ship is bought by a rival company and her bottom structure is strengthened so that she can be taken out to sea. The ship is towed to her new home (possibly California next to the Queen Mary or back to England or possibly Abu Dhabi beside the QE2). The company spent so much money getting it there that they file for bankruptcy and the ship becomes a liable asset and is auctioned off in one of the greatest sales in modern history. Bidding for the Titanic. "Do I hear 2 billion dollars?.....Sold to the gentleman at the back.....The next item for sale is the SS United Sates."
The Titanic is then photographed and scanned inside and turned into a virtual reality simulator. It becomes profitable for a short time, but ticket holders are now less enthusiastic about flying over to board the actual Titanic and booking a night as the Titanic VR experience is much for affordable and it has the added bonus of changing into different themes e.g. modern times, or 1912. There are plans to turn the ship into a workable passenger liner again, but the changes made to her appearance discourage investors and the company loses so much money that they are forced to sell the ship again. During the transition between owners the Titanic is intentionally sunk or burnt down for insurance. An Inquiry is held into the Titanic's sinking (again) and there is blame on many sides, but the mystery continues.
The good news is that somebody scanned every inch of the ship and there are plans underway to build another Titanic using the original specifications that were taken just before the Titanic sank again. The original ship is ultimately left on the seabed and becomes a new home for beautiful marine life and people are already diving to see the ship and marvel at her long history.
I have it on best authority that an attempt was made to turn the hulk into a museum of sea faring adjacent to London Bridge in Arizona. That failing, the ship rusted for a while on the beach before ultimately being sent to the breakers where the steel was made into razor blades which were sold primarily to Hobbits and maried Amish men around Shipshewana, indiana, where crates of rusty blades are sometimes offered at the weekly livestock auction.