Doing a new implementation that preserves all of the features of existing code in all scenarios is really hard. The re-implementation team never knows all the scenarios that matter.
Is AI going to fix this? AI won't know all the scenarios and corner cases, either.
The pool of C software worth rewriting is shrinking. There are the few too-big-to-rewrite projects that will never move, but everything else is either getting rewritten, or has more modern replacements already written directly in Rust.
I can't vouch for LLM-assisted rewrites. The results can be randomly dodgy regardless of what you're writing or rewriting. I suspect we'll get plenty more LLM rewrites anyway, and people will just compensate by sending LLMs hunting for bugs by brute force.
It's a typical C mindset that rewriting programs creates new bugs, because it takes years to "battle test" and shake bugs out of a C program. In my experience rewrites in Rust uncover latent bugs of C programs when they finally get checked lifetimes, useful type system, enforced error checking, etc.