I've seen ancient codebases that you need to be blessed by a priest to even touch but they keep chugging away and having new features added. I wouldn't hold my breath for a collapse, just a quagmire that we continually have to wade through to get anything done.
Isn't it also true that the deeper and thicker the quagmire, the more tokens one will have to use to wade through it?
This seems like a path to eventual LLM lock-in once the codebase gets messy enough. These things could end up being like 0% interest credit cards for technical debt. I guess it all depends on how the token usage scales over time. My guess is it will be steeper than linear.