We won't have understanding of our code, similar to how we don't understand the machine language being generated by our compilers now.
We will be using our intuition about GPT to bring into being fully designed and integrated systems with 10 paragraphs at the prompt.
Which could in the end greatly increase the influence of a programmer in a given organization. Our role will be a softer, almost cyborgian one.
But this will indeed require the destruction of all that came before it. Questions like "but does it work with this 3rd party API, or this platform?" must become irrelevant for this future to happen.
A bit similar to how the web destroyed mainframe, perhaps, by first creating its own compelling world, then making the mountain come to it.