In a recent tweet of a Square-Enix producer, he mentioned that a Final Fantasy IX on the PlayStation Network is possible to arrive on the PlayStation Network very soon. Since both Final Fantasy VII and VIII are now on the PlayStation Network and have been selling like hot cakes, the release of Final Fantasy IX is not impossible at all. According to the tweet of Shinji Hashimoto, a lot of people have requested FFIX to appear on the PlayStation Network and starting next week, he will propose that idea to the next board meeting to be considered.
The news currently applies on the Japanese PlayStation Store as of now. However, once the proposal has been passed, it is no doubt that North America and Europe will receive this classic as well on their PlayStation Network.