At MIT, mostly what I did was documentation. I sort of read things. Wrote some descriptions of various aspects of the file system. Did not really do very much programming at all. At least on Multics.
C was already implemented on several quite different machines and OSs, Unix was already being distributed on the PDP-11, but the portability of the whole system was new.
UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity.
Over the past several years, I've been more in a managerial role.
I'm just an observer of Java, and where Microsoft wants to go with C# is too early to tell.
C++ and Java, say, are presumably growing faster than plain C, but I bet C will still be around.