Other fields certainly are not immune to the declining value of knowledge capital. Ask any older auto mechanic how much his knowledge of carburetors is worth these days, just as one example.

Any profession that works with continually advancing technology is going see this effect. Granted it does seem more pronounced in the computer field... but yet there are some areas where you don't see it so much. If you are a "C" programmer, everything you've learned over the decades is still relevant and useful. Unix system administration is another example. Yes things change, but a lot of the old knowledge, e.g. tools like sed and awk are still plenty relevant.

Also the author doesn't acknowledge that a lot of knowledge transcends language. Knowledge of data structures and algorithms carries over as language fads come and go, and there's a lot of core knowledge you don't lose in the transition from one to the next.

I've been in the software profession for over 20 years, and what I've noticed is that the stuff that fades away quickly is the stuff that sucked from the get-go. COBOL? Sucked, now mostly gone. Mainframes? Sucked, now mostly gone. Visual BASIC? Sucked, now mostly gone. C? Dangerous, but powerful... still around. Unix? Pretty fun, very flexible, still around. SQL? Still one of the best ways to work with data, still around.