The size difference is like Sutter Buttes versus Mahalangur Himal, so unless it's accelerating at the speed of light, C++ will be dwarfing rust's usage for many years to come.
This is the umpteenth time large tech companies have sponsored C++'s successor. Go was famously created to eventually supplant C++ at Google (or more specifically, solve the issue of long build times). Over a decade later, C++ is very much still in heavy usage at Google.
If I were a bettin' man (or if I were trying to increase my general employment odds), and the choices were between Rust or C++, I would pick C++.
That being said, if I were in a comfortable financial position, wanted to scratch a nerd itch, and have fun programming again, I would absolutely pick Rust over C++.
I certainly do not disagree that C and C++ will be in general usage for a long time, if not forever. However, because the industry is still growing, the proportions change, even as the total number grows in size. C and C++ do not have to die, or even shrink, to become a smaller part of the overall pie, and Rust does not need them to outright die in order to grow and thrive.
I agree with you that this is not the first time languages have tried to encroach on the last bastions of the spaces where C and C++ have not yet been ousted as the default choice, but Rust is actually gaining traction in production use-cases in those spaces, unlike many of those languages.
This is the umpteenth time large tech companies have sponsored C++'s successor. Go was famously created to eventually supplant C++ at Google (or more specifically, solve the issue of long build times). Over a decade later, C++ is very much still in heavy usage at Google.
If I were a bettin' man (or if I were trying to increase my general employment odds), and the choices were between Rust or C++, I would pick C++.
That being said, if I were in a comfortable financial position, wanted to scratch a nerd itch, and have fun programming again, I would absolutely pick Rust over C++.
But those are two very different scenarios.