I think that the spread of capability and effectiveness between the best and mediocre will continue to be several factors and might even increase as compared to today.
I can’t see any way it would be less than 2x.
I don’t think you’re giving yourself enough credit for understanding enough about system design to be able to effectively prompt and guide the LLM.
John Carmack* is going to be at least twice as good at making a game with LLM coding assistants as a mediocre prompt engineer will be. Guido van Rossum* and Rich Hickey* will be over 2x a mediocre prompt engineer at language creation. Linus Torvalds* will create the first version of git far faster than any mediocre prompt engineer (who will never complete that task). And on and on…
* replace with whomever you think is “best” in the field you’re comparing.