We don’t need anything close to AGI to render the job “software engineer” as we know it today completely obsolete. Ever hear of a lorimer?
The other possibility is, as you say, progress slows down before its better than humans. But then how is it replacing them? How does a worse horse replace horses?
Progress in LLMs will not slow down before they are better at programming than humans. Not “better than humans.” Better at programming. Just like computers are better than humans at a whole bunch of other things.
Computers have gotten steadily better at adding and multiplying and yet there is no AGI or expectation thereof as a result.
All the current AI success is due to computers getting better at adding and multiplying. That's genuinely the core of how they work. The people who believe AGI is imminent believe the opposite of that last claim.