George had the broadstrokes of the PT laid out by the end of making the OT. (Lava planet, ROTJ Vader seeming much more like Anakin Skywalker from the prequels in dialogue and characterization, etc.)
Now, I’m not sure what your getting at with this sentence. Are you one of those people that think he had planned for the PT to exist the whole time? For those that use “that’s why he called them Episodes V and VI” as an excuse to think this, that is not why he originally used the episode numbers. He used them in yet another way to recreate the feel of coming into a theater to see some Flash Gordon serials, and you just came in the middle of the story. And ROTJ Vader wasn’t any closer to PT Annie than in the first two.
George had some ideas for the PT in 1980 but I’m sure whatever ideas he had were long gone by the time the mid - late 90’s came around