That's assuming you're doing the same thing you used to do 20 years ago.

I mean even with new technologies, if you end up building sophisticated CRUD interfaces with language FooBar 20 years from now, you can't really complain about it.

People who managed to differentiate themselves in CS over the years moved to stuff like computer vision, natural language processing, designing programming languages, optimizing virtual machines, designing protocols or mixing their knowledge of CS with another field.

Very advanced stuff which takes years (if not decades) to master and to write/build properly.

So, I would only worry if 20 years from now, you're still solving the same problems but with a cuter UI and a faster machine.

PS: Should have used "one" instead of "you". I don't mean "you" ;-)