Rockstar Games announced GTA San Andreas today, currently slated for October 19, 2004 release. It's likely going to be the same engine, and targeted exclusively for PlayStation 2. Having just finished Vice City a few months ago, I could easily spend another few months playing through another Grand Theft Auto.

From their news release posted today:

"Rockstar Games is pleased to announce Grand Theft Auto: San Andreas, the next iteration in the globally successful Grand Theft Auto franchise. Developed by world-class designers Rockstar North, Grand Theft Auto: San Andreas will be available exclusively for the PlayStation®2 computer entertainment system and is expected to be in stores in North America on October 19, 2004 and in Europe on October 22, 2004."