The "ceiling" is the fact that no matter how fast AI can write code, it still needs to be reviewed by humans. Even if it passes the tests.
As much as everyone thinks they can take the human review step out of the process with testing, AI still fucks up enough that it's a bad idea. We'll be in this state until actually intelligent AI comes along. Some evolution of machine learning beyond LLMs.
Don't give them any ideas! We don't need Dumb Restrictions on Motors.