Right now I think there is an edge to how you construct prompts and config files. There is a large difference between "modify f() to do..." and "modify f() to do... Review the current variables and make sure they are still used consistent with their naming. Look for unreachable and dead code. Examine callers and called functions for side effects from the introduced changes...".
I don't think that will make much difference in a year.
I'm increasingly convinced of the opposite. IMO Fable was pretty similarly capable for my day to day work as Opus.
I think there's a pretty good chance that we've reached the point of diminishing returns, for our specific use case.
There are still like a billion other (more difficult) use cases to be tackled, but I think "generating code" has gotten really good to the point where the other bottlenecks will prevent further exponential progress on this specific task.