No foot in mouth that I see
I'm the same age as my Suburban, so one can only hope that I will live to 75
Parts are getting reproduced more, mainly for the restoration hobbyist.
Everything else is pretty interchangeable, so I think as far as old Chevy trucks go there will never be a problem with getting parts as years go on.
Locating them, and paying affordable $.. Now that will always be the challenge, and part of the thrill of the hunt when building something old.