Once you can load up a full codebase into an LLM I'm hoping the cost to update client code is significantly reduced. Then you could focus on evolving the design without all the grunt work.
I'm also betting on this, that one day I'll be able to dump a codebase into an LLM and it will clean up the code. Not rewrite it, not restructure it, just clean it up. Remove unused code and comment it sensibly. Maybe also suggest some tests for it and implement them separately.
Comments should be based on intention. If I, as the programmer, am writing a piece of code and feel like there's something that I need to communicate about my intention in writing this, then I should. But if it's just surface level analysis, comments are just noise most of the time.
Copilot already does this, at least for individual chunks of code (and text, for that matter). Not for a whole codebase, but I think that's going to be a matter of time.