In my opinion, the two languages are going to co-exist for a long time. C has billions of lines of legacy software written in it… In recent news, COBOL developers were sought after in order to update existing COBOL software, so the same thing will happen with C, perhaps to the end of humanity (I have become pessimistic as to humanity's future).

There are pieces of software that should be given priority for a rewrite in Rust, but most of C software is never going to be rewritten, because there is simply too much of it.

Therefore, even if C did not have any advantage of its own over Rust, there would still be legacy software to maintain and to extend.

The advantages of C include that sometimes, an embedded processor with a proprietary instruction set is provided by the chipmaker with its own C compiler, which is the only compiler supporting the instruction set; that C is still currently used to write the runtimes of higher-level languages (I'm familiar with OCaml, but it isn't too much of a stretch to imagine that the runtimes of Python, Haskell,… are also written in C).