> Perhaps we would still be exclusively writing C today for new languages' code could not been synthesized as easily or conveniently.
I'm not actually sure that would be a bad thing? All the reasons that immediately come to mind to move away from C have to do with ergonomics and safety, the latter largely being a product of the former IMO. If an LLM can ingest my entire codebase and do 90% of the work to get me to the changes I need doesn't that obviate the majority of the motivation to change languages in the first place?
If we get a completely autonomous AI it probably won't program in C (or any other human-understandable language).
If it still programs in a human readable language, that means people need to review the code, at least from times to times. And it's much easier to review modern languages than C.