The English localization is almost done. But the Japanese build of Final Fantasy XIII, shown off at Gamescom, gives you a good idea of what to expect in the gameplay when the title releases next year for Xbox 360 an PS3.
FFXIII's developer notes the game's combat mechanism employs something they call the "paradigm shift" engine, which allows you to assign objectives to party members as a strategic choice. Stackable action commands will also lend an action game pace and feel to the game.
There are two more videos at GameTrailers, featuring an interview with FFXIII's director and producer.