You're right about D, but Rust is drawing some people away from C and C++. Something may emerge that will do the same on the JS front-end. In fact, I'd say that the TypeScript/React combo is more susceptible to being replaced than C and C++ are. There are many large C/C++ codebases that represent many man-years of work and won't be rewritten or thrown away any time soon. JS front-ends don't have that kind of longevity. Think about how many web startups just fizzle out, and their code just goes away.