Based on the actions made to the SS Norway and the SS Independence by NCL/Star Cruises, it is very doubtful that they will spend the kind of money that's needed to make the Big U sail again. In fact, the opportunity for that has passed when the ship's fittings and equipment was sold at auction in 1984.
Had Mr. Hadley simply given the Big U a new paint job and upgraded its safty requirements, I believe that the ship would be sailing today. Although, there would have been many changes to her, both inside and outside, like the SS Norway.
If NCL decides to put the Big U into service again, the ship's powertrain would be gutted down to make way for a new disel plant. The one element that has kept the ship with us today would be lost forever. The ship's Naval powerplant was the one thing that makes this ship so special. The Cold War relic. No; I no longer have faith the NCL will ever refit the Big U.
The only option I see for the ship is to make it into a museum/hotel in New York City.