I'm definitely not an AI skeptic and I use it constantly for coding, but I don't think we are approaching this future at all without a new technological revolution.

Specifications accurate enough to describe the exact behaviors are basically equivalent to code, also in terms of length, so you basically just change language (and current LLM tech is not on course to be able to handle such big specifications)

Higher level specifications (the ones that make sense) leave some details and assumption to the implementation, so you can not safely ignore the implementation itself and you cannot recreate it easily (each LLM build could change the details and the little assumptions)

So yeah, while I agree that documentation and specifications are more and more important in the AI world, I don't see the path to the conclusions you are drawing