Lucas's original plan. He would release STAR WARS in 1977 and release many sequels depending on the success of the first one. A total of 9 episodes were planned with STAR WARS being Episode 1. However, by 1980 when ESB had been completed, he realized the potential of the Anakin Skywalker story so he decided to label ESB as Star Wars Episode V - The Empire Strikes Back. Many movie-goers were suprised and confused by this title. In 1981, he retitled STAR WARS as Star Wars Episode IV - A New Hope. When making ROTJ, he decided to can the idea of episodes 7, 8 and 9. Either due to lack of interest, or lack of story. He crammed the last 4 episodes into one. In 1983, he released ROTJ as Star Wars Episode VI - Return of the Jedi. So as you can see, there was never any plans to make a prequel trilogy. While he did have the basic Star Wars story outlined, he never planned for prequels to be made. Lucas does changes things as he goes along.