True a lot was cut; however sith wise; From korriban descendants to the sith clans to bane's rule of two line all the way down to sidious are still cannon; The books; The book of the sith The jedi path The bounty hunter code The new essential guide to weapons and technology Are all still cannon from what ive been told by gossip around some forums. (They mostly reference and site materials only from the movies, new tv series, kotr and up coming stuff likely to be used in rouge one and the force awakens)