DQIX seems to be leaning toward the action-RPG end of the role-playing spectrum, as the traditional random battles have been replaced by a Chrono Trigger-style "see the enemies in the field of play" approach. As all four characters' motion and actions are controlled independently, Square-Enix is pushing a four-player cooperative mode (via Wi-Fi? We still don't know) into the game. The players need not stay together; for instance, one player could journey into a nearby cave in search of treasure, while another can head back to town to pick up some much-needed curative supplies. Sounds simple, yet cool.
Stylus control will be implemented, though details remain sketchy; Dragon's Quest IX will be released in 2007, and details remain awesome.