All of those "things" will be plugged into an AI and one senior technologist will be able to write a detailed functional description of a system in natural lang

All of those "things" will be plugged into an AI and one senior technologist will be able to write a detailed functional description of a system in natural language, domain models, with data points, and an AI will write, test, integrate, and deploy production level code. Given that the severe limitations of the current state of the art (as we've seen from from how trivial is to show that these systems are basically spouting nonsense, and certainly have no meaningful understanding of the world we actually live in); and that this 100 percent waterfall model of software creation you describe has never worked in the aforementioned actual world that we live in - How, exactly, do you "know" that the above will come to pass?