That treatment page of Episodes 7-12 completely blank always cracks me up. Good planning there, George.
In all seriousness, I am sure he did actually come up with some ideas for those episodes.
For instance, I remember him explaining that each trilogy was on a different philosophical theme.
Episodes 1-3 was the POLITICAL TRILOGY.
Episodes 4-6 was the SELF-ACTUALIZATION TRILOGY (the hero's journey)
Episodes 7-12 I don't remember.
There was a comment made by somebody, though, who read the treatments for 7-9 back in the day and thought that they were the most exciting/dramatic movies of the entire series.
Of course, that may have been the now-obsolete versions with Luke's other sister, the Emperor revealed, and etc.