GPT-4 has a model capable of using around 50 pages of written text worth of tokens (32,000) not sure exactly how many lines of code that translates to but it’s a lot. GPT-3 can use 4k so that’s a huge increase, the next version could be even larger and there are other ML techniques that allow for massive context lengths. Copilot already does a good job of refactoring code and knows enough about your code base to use your functions and methods. So what the other commenter said does not sound impossible to me.