This is one of the most persistant Star Wars rumors ever concocted by a journalist. Yes, that's right, a journalist. Some reporter back in the 70s asked George Lucas whether or not there would be trilogies preceding (Episodes I, II, and III) or following (Episodes VII, VIII, and IX) the original Star Wars trilogy (Episodes IV, V, and VI). Somewhere in there, the journalist screwed up and the rumor started going around that Star Wars was originally planned to have nine parts. All of this was confirmed in the Lucas-approved Star Wars film class I took at USC in Spring 2000 with the renowned Dr. Drew Casper. Even if you don't believe all of that research and Lucas himself, here's some food for thought:

1. The Star Wars saga follows Anakin Skywalker above all others. IT IS HIS STORY. It begins and ends with him. (Yes, Artoo and Threepio are in all the movies as well, but it's not about them.)
2. The rumored main characters of Episodes VII-IX were Han Solo and Princess Leia's kids. Don't get me wrong, I like Jaina, Jacen, and little Anakin, but they are still Solo kids and are less attuned to the Force than their mother and uncle, though it is still strong with them. At any rate, it's a bit late in the saga to suddenly turn it over to three completely new characters. Yes, there are lots of new characters in the prequels, but there are still the carry-overs to the later trilogy: Anakin Skywalker, Obi-Wan Kenobi, Yoda, and Emperor Palpatine, at the very least. Besides, if Luke and Mara are going to have kids (well, or more in addition to little Ben), it only makes sense to follow the male Skywalker line.
3. Lucas has said that one of the reasons he started working on the prequel trilogy when he did was because he knew that making a ten-year commitment to the rest of the saga would be more difficult if he was any older, so the time to act was then.

The closest that Episodes VII, VIII, and IX will ever get to being made is in the form of the Timothy Zahn Thrawn trilogy.

And if you still have any doubts as to the lack of truth to this rumor, remember: