When George Lucas redid the original Star Wars trilogy in 1990, on VHS, they included an interview with him and Leonard Martin, I believe. In that, he talks about his big book of Star Wars, and how he is going to put out three new Star Wars movies, take some time off, and make the last three Star Wars movies, to start, and finish, the story of Luke, Leia, and the rest. So, the "rumor" of the third trilogy has been around a lot long than The Phantom Menace. And they could be waiting for GL to start casting for the next movie.
When everything else fails, CHEAT!