BioWare's latest info update for The Old Republic reveals two "advanced Jedi" classes will be playable: the Guardian and the Sentinel. Guardians are more defence-based and leadership-based. Sentinels bring two lightsabres and a whirlwind of damage.
The official blurbs on both classes:
Guardian A wall between the good people of the Republic and their enemies, the Guardian stands firm in the face of overwhelming odds and dares opponents to attack. Perfect concentration and use of the Force allows smooth movement even in heavy armor—making the Guardian a hard target to take down. Leaders on and off the battlefield, Guardians are known for inspiring allies to amazing feats, making them invaluable for conflicts of any size.
Sentinel Control and focus are the hallmarks of the Sentinel. Through years of training the Sentinel learns the art of using two Lightsabers simultaneously to create an intricate web of damage that is almost impossible to evade. Manipulating the Force, the Sentinel can see holes in the enemy defence, potential flaws in their own technique and how best to plan for both.
Check the link for more details, and enjoy the screens below.