preceding c, there was a large, complex, portable algol-family language capable of handling a range of applications similar to c's, called pl/1. if you read 'the elements of programming style', from about the time c was born, many of the examples are in fortran; most others are in pl/1. gary kildall's first job working on microcomputers was at intel writing pl/m, a cut-down pl/1 for microcomputers, for which he wrote cp/m, from which ms-dos grew. ibm's database db2 is still written in a dialect of pl/1 called pl/x. one of wirth's first languages was a thing called pl/360, which was a version of pl/1 with extra low-level facilities for bootstrapping a better language
in short, pl/1 was very widely used and highly influential, even though it's almost forgotten today
and that's because it kind of sucked. compiling it required a large computer and even then was slow. even at the beginning, it was highly complex, so learning it took a long time. this got worse over time as more and more features were piled onto it, often as ill-advised efficiency hacks that then couldn't be removed, because people's programs depended on them. because it was highly complex, and there were a lot of surprising problems that resulted from complex interactions of all its complex features; compiler developers improved this situation significantly by working hard to provide better error messages, but that only diminished the problem rather than eliminating it
the preceding paragraph describes rust exactly as well as it describes pl/1, so if someone succeeds in producing a c-like small, simple language that provides enough of rust's unique advantages (which are indeed very compelling) i expect that it will replace rust
i doubt it will replace c tho