You will always get much, much, MUCH better performance from something that looks like assembler code than from having an LLM do everything. So I think the model of "AIs build something that looks recognizably like code" is going to continue indefinitely, and that code is generally going to be more deterministic than an AI will be.

I'm not saying nothing will change. AIs may be constantly writing their own code for themselves internally in a much more fluid mixed environment, AIs may be writing into AI-specific languages built for their own quirks and preferences that make it harder for humans to follow than when AIs work in relatively human stacks, etc. I'm just saying, the concept of "code" that we could review is definitely going to stick around indefinitely, because the performance gains and reduction in resource usage are always going to be enormous. Even AIs that want to review AI work will want to review the generated and executing code, not the other AIs themselves.

AIs will always be nondeterministic by their nature (because even if you run them in some deterministic mode, you will not be able to predict their exact results anyhow, which is in practice non-determinism), but non-AI code could conceivably actually get better and more deterministic, depending on how AI software engineering ethos develop.