The suggestion was to have some AI system “fix” the code. They are reporting that they’ve found lots of bugs. Are they even claiming to have exhaustively found all the bugs? I don’t think even the most optimistic pitches would claim that.

I’d expect patching existing codebases to be an eternal treadmill as better models come about.

Who's suggesting that? They're sending reports to projects to fix. It's up to the projects on how they fix them.

No, I don't think all bugs are fixed. The point of the project (glasswing etc) was to fix as many as possible in the core software the world runs on before the capability to find vulnerabilities is available to everyone (black hats included). Which may only be a few months.

I do think everyone expects it to be an ongoing treadmill: models get better, find better vulnerabilities, etc.