I suspect we'll see combinations of symbolic execution + fuzzing as contextual inputs to LLMs, with LLMs delegating highly directed tasks to these external tools that are radically faster at exploring a space with the LLM guiding based on its own semantic understanding of the code.

I'm with you, I expected this to be happening already. Funny enough, I guess even a hardened codebase isn't at that level of "we need to optimize this" currently so you can just throw tokens at the problem.