I'm not saying more code won't be produced, I'm saying companies might only want and make money off a certain number of systems with a given amount of code, and therefore they'll need to employ fewer developers to create that code, if the productivity enhancements are borne out.
For example, say you're the CEO of one of the many many companies that view development costs as an overhead. Your CTO comes to you and tells you "hey we've just 10x the productivity of all our developers", do you think that conversation leads to the CEO saying "great hire more developers"?
(speaking at least for myself) I'm not suggesting this is a good outcome, more that having seen the way many companies handle development and IT, it's quite a likely one.
FWIW I'd agree that (for now at least) it's challenging to get LLM/AI created code to avoid security vulnerabilities without careful prompting and review. Whether that's a fixable problem or whether it'll just generate mountains of new CVEs, bug bounties and ransomware attacks, remains to be seen.
For example, say you're the CEO of one of the many many companies that view development costs as an overhead. Your CTO comes to you and tells you "hey we've just 10x the productivity of all our developers", do you think that conversation leads to the CEO saying "great hire more developers"?