It's already going away for me in a sense as I build up a library of AGENTS.md and Codex skills. I see no reason such things won't get baked in at the agent layer so that domain specific rules and such are automatically applied when appopriate.
I'm not sure if you're ahead of me or behind me on this curve, but fwiw, my experience has been that we have now encoded everything that is useful in the various markdown files and have reached the point of diminishing returns on this, with more powerful new models making noticeable but not revolutionary improvements as they come out.
You're essentially making the case here that your work is now automated into a set of one-shot actions that can be performed by an AI model and your job has become to selectively apply these actions. That says either a) we don't do the same work, and instead you're doing some kind of low level devops function that I've only ever seen in rare cases where a human isn't needed anymore, or b) you've vastly oversimplified the software engineering you're doing.
Sophisticated chain of reasoning LLMs like ChatGPT have baked in some natural language operations and they make it so i can create at a higher level of the language expression stack. But I'm still formulating my own expression. There's no conceivable path I can see where an improved model is going to be able to do what I do. I think that is clear from my ChatGPT threads at least.