You'd think they'd keep at least a couple of them on government service as research aircraft.
Considering how high they can go and their speed, they would make excellent high altitude research bird. Just re-engine them with a more modern engine, remove the seats and strengthen the fuselage structure a bit more and you could do whatever you liked with them.
Can you imagine training astronauts in a "Vomit Comet" that could hit mach 2 and go that much higher than the things currently used for the purpose?
They may not have been real roomy for passengers, but with the seats out there's plenty of room for all sorts of scientific instuments and gadgetry.
I understand they are all still generally structurally sound, so they should be kept up in the air as long as they can be.