If it helps, this likely is coming. I think we have a tendency to mentally move the goalposts when it comes to this kind of thing as a self-defense mechanism. Years ago this would have been a similar level of impossibility.
Since all a codebase like that is is a kind of directed graph, then augmentations to the processing of the network to allow for the simultaneous parsing of and generation of this kind of code may not be as far off as you thinking.
I say this as an ML researcher of coming up and around the bend towards 6 years of experience in the heavily technical side of the field. Strong negative skepticism is an easy way to bring confidence and the appearance of knowledge, but it also can have the downfall of what has happened in certain past technological revolutions -- and the threat is very much real here (in contrast to the group that believes you can get AGI from simply scaling LLMs, I think that is very silly indeed).
Thank you for your comment, I really appreciate it and the discussion it generated and appreciate you posting it. Replying to it was fun, thank you.