First of all, past trend doesn't predict the future.
And if it did, then the answer would be nothing will matter in 20 years. Not just "no programming language," but nothing.
No one can predict the future least of all humble extrapolation line.
And specifically, why would Rust be a better choice than C or Zig when the LLMs get good enough to just write memory safe code in unsafe languages (they are already pretty good at finding memory safety bugs).
IMHO for code generation, different things start to matter (like fast build times, while 'convenient highlevel abstractions' become less important).
If you learn how to use arena allocators and in general use modern techniques, you don't need global reasoning to write correct memory management code pretty much never.
If your code is a RAII and abstraction maze, then yes, you will probably need global reasoning, but that's not the case with Zig.
Rust is a great language with some great killer features.
It does not need consistent propaganda preaching how it's a better choice than "insert other language".
Every system programmer is aware of Rust and it's pros. Doesn't mean it's a language that fits the use case, project, constraints and even preferences. It's not just about generating code, it's also about reading it and maintaining it.
Thus some people just prefer alternatives, be it C, C3, Odin, Zig, Jai or whatever else there is.
You said it yourself, it's selling point is "nicer C", so it's for people that don't want to write Rust or C++ but a nicer C.
Indeed. There is an irrational urge in some folks to become language-missionaries. Usually such folks have gained expertise in that specific language and want to protect and expand their turf. There is a wide-range of software usecases requiring a variety of tools and no one language fits all.
Amusing side-note. xai was all-in on rust for their ai-stack back in 2023. But now, spacex controlled xai is apparently coding ai in C - perhaps with the attitude that if a language is good enough to control rockets it is good for ai.
But what they miss is that other people think differently than them. Other people will feel let out of prison by a different language.