As the loading screen in KOTOR 1 says, "True Sith disappeared years ago. The Sith now are just followers of their belief," or something like that. I believe the Sith is some sort of force-sensitive race, like Visas' race (can't remember the name of it).
Anyway, I want to see more lightsaber forms in KOTOR 3, and have them all look different from one another. Also, a Jedi should excel in one of them, not constantly having to switch between them.