Nassim Taleb has this nice heuristic that says that the expected future life of something is proportional to how long it's been around.
So ASCII text will outlast HTML, because it preceded it. And HTML will outlast JavaScript.
So you might guess that Unix will outlast even the web. I doubt that a deep knowledge of Unix will become obsolete in the lifetime of anyone alive today. We might ubiquitous computing and networked sensors and AI, but it seems like all of those things will be running on Unix.
(note: this is of course a heuristic)
Lisp? We're all reading HN which is written in some Lisp dialect. There are also quite a few Clojure devs in here (including me) and a few using other Lisp dialects (and participating in flamewars about what a true Lisp is or is not). Don't know if it counts ^ ^
And then not 1969 but 1976: daily Emacs user here...
I have yet to do much with Clojure, mainly because I'm not really in the JVM ecosystem. But I think its focus on immutability is a great contribution to Lisp and will last a long time. It's an idea that transcends a particular implementation.
What changes are lot are the actual frameworks and libraries. E.g., while Java is twenty years old now, Hadoop, JAX-RS, Hibernate, etc. did not exist then. And while Java will probably still be in wide use in twenty years, those libraries and frameworks will have been replaced except in legacy code.
I think the only 'platform' that has been stable for ever is UNIX. People are still using libc, POSIX (ok, SUS), etc.