I can only speculate, but my guess is that this limit is pretty fundamental, yeah. However capable the models get, they can't read your mind. The kind of iteration you have in mind is difficult because they don't have a basis to iterate upon; to the extent that they could pretend, that gets into what people have been calling "taste".

And even if they somehow got better taste, it wouldn't be your taste. If that were acceptable, why bother prompting anything in the first place? At that point the system might as well choose its own projects entirely. But I don't think humans would want to live in that world; even if not paperclip-maximized, we'd eventually become an underclass.

That's assuming basically unlimited capacity for the models to get more powerful. If there are limits (and I hope there are!) then it'd be even more certain that projects continue to require human guidance.

But even despite that, I hope I don't sound AI-psychotic if I suggest: the models are capable of at least assisting with that spec-writing and decomposition.