Arguably the PM role only exists because SWEs don't want to do PM work, and the industry acquiesced to this because SWEs are in very short supply - if you could hire a layperson (sorry) to take a few hours of non-technical work off a SWE's plate, it is worth it.
In a (hypothetical; not quite there yet) world where SWEs are in surplus, there is no reason to have PMs.
The really eye-popping efficiency gains from LLM coding won't come from doing the coding faster but from consolidating the PM, SWE, and QA/SDET roles under the same person. Then you'll start seeing startup/indie level productivity-per-person inside large organizations. Imagine Google is like 50,000 Pieter Levels.
The concept of a large organization doesn’t even make sense in this model. How do you make decisions? How do you coordinate? What is Google when you have 50,000 individual silos?