That date would indeed be the Princess hulls. The BOAC ones went in the years after they shut down. Aquila Airways then took over Hamble and ran a range of leisure destinations for a few years with a number of aircraft, but gave up in 1958. Their last aircraft were ferried out to Lisbon for a start-up they were associated with which never got going, they were finally scrapped in the early 1970s.
There are still a fair number of preserved Short aircraft around the world, quite a number of which I have been into (or touched). Last one I saw flying was overhead the Thames in London in about 1986. None of the big US boats were kept, but worth mention to aficionados is the Flying Boat museum at Foynes in Ireland, near Shannon, which has a very well done full size reproduction of a Boeing 314 boat (minus the outer wings) which you can walk around inside. Must have been quite an effort to build. It's here
https://www.google.co.uk/maps/@52.61...7i13312!8i6656