Unix has retarded OS research by 10 years and linux has retarded it by 20.
C++ and Java, say, are presumably growing faster than plain C, but I bet C will still be around.
The number of UNIX installations has grown to 10, with more expected.
I can't recall any difficulty in making the C language definition completely open - any discussion on the matter tended to mention languages whose inventors tried to keep tight control, and consequent ill fate
The only way to learn a new programming language is by writing programs in it.
I fix things now and then, more often tweak HTML and make scripts to do things.