For some reason that I am unable to explain, I am somewhat optimistic about SS United States. Not necessarily as a sea-going ship again, but as a static fixture somewhere.
I noticed that NCL offers lots of cruises from NYC. Suppose, as has been postulated numerous times, SS US is berthed alongside Intrepid, just a few piers away from the ones NCL uses. NCL could then build up the interiors and convert her to a hotel/museum (also not an original thought). The hotel portion can then be used for pre- and post-cruise packages for those sailing with NCL...perhaps even offering check-in... similar to what Carnival does with Queen Mary.
This would also be consistent with NCL's repeated announcements about how they will soon have the youngest fleet in the business. If the ship isn't sailing, I suppose she's not part of the fleet.
Just a few thoughts, for what it's worth...