KOTOR 2 will be based five years after the original KOTOR. Because of the player's ability to change the outcome of the original KOTOR, the plot of KOTOR 2 will not be directly related to the first game. Instead, a series of questions will be asked at the beginning of the game that will evaluate which ending (dark or light) the player wants to play after. The rest of the game will be affected by these answers.
In KOTOR 2, you will play as the last known jedi of the order, as it has since disbanded due to the stress put upon it by Darth Malak's reign of terror and a civil war. You will start the game as a jedi, though, due to the fact that you are an "outcast," you have become somewhat seperated from the Force. You will not start out with all of your powers, nor will you receive a lightsaber.
Though the developer Obsidian doesn't wish to reveal much more about the plot, three characters out of the ten that will be available in your party have been revealed. They are T3-M4 (returning), Krela (an older Jedi), and Atton Rand (macho man).