Zig won't be affected by Bun potentially moving to Rust, the language has been growing rapidly and one of the main proposals of Zig is "maintain it with Zig". It's ability to integrate with existing C code bases, as well as be a drop-in build replacement, has widespread use.

In addition, the link in the comment you replied to explains why the PRs Bun opened to Zig would have lowered the quality of the compiler and how Zig has achieved even greater speedups, with more widely applicable features like incremental compilation and the self-hosted backend.