My thesis has long been that it's impossible to replace C++ with a single language. C++ got into the trouble it has because it permits any and all development to occur within its walls. The C++ committee cannot make any decision without alienating some niche C++ industry that nevertheless represents at least hundreds of millions of dollars per year. The result is a jumbled mess of mismatched and incompatible features that provide a combinatorial explosion of hiding places for surprising and dangerous interactions in otherwise innocent looking code.

Rust (and insert any other language here) can only kill C++ by being C++.

However, we're seeing quite a lot of systems language development over the last decade and a half. Which is surprising coming from any sort of money making venture. To create a serious language, you're signing up for a decade of hard work at a minimum just to get your foot in the door. Then an endless parade of technical and community building issues to wade through, forever.

C++ cannot be killed off by one language, but it can be killed by a dozen or two languages. So we're seeing Rust, Hylo, Vale, P, Odin, Zig, Jai (do we have a release date for that one yet?), Carbon, Swift, Go, and even the newer language releases of C++ is trying to kill off old C++.

A lot of entities are looking around the room and asking themselves "how do we deal of this C++ thing" and then deciding to commit to the seriously non-trivial endeavor of creating a new language from scratch.

Eventually, C++ will be relegated to a historical footnote and niche application. Although, I'm not going to be surprised if this takes another 50 years and half a dozen new languages on top of what we're already seeing.