I've been studying the nature of the Sith, specifically the Rule of Two that Darth Bane put into place to preserve the future and the secrecy of the Sith.
As far back as the events of Star Wars: The Old Republic, Sith were actually very prolific. Of course, their characteristic greed for power proved to be their downfall - what with all of the back-stabbing and betrayal that was (and inherently is) prevalent in Sith culture.
Fast forward to the events of the Anakin Saga and you only ever really see two Sith in any sort of prominence - a Master and an Apprentice, as the Rule of Two dictates. There are exceptions, but they quite frequently devolve into in-fighting and betrayal - par for the course.
Now, I haven't studied much of the Extended Universe that takes place beyond the events of Episode VI. With the deaths of Vader and Sidious, I presume a lot is left in flux. Keep this ignorance of mine in mind when I ask the following questions:
Would the Rule of Two remain intact after the death of the last Sith duo?
How might multiple Sith exist in parallel if the Rule of Two wasn't traditionally enforced?
What kind of room is there for Sith outside of the Rule of Two? There seems to be plenty of force-wielding Dark-siders with lightsabers beyond the Two, both across the video games and in the screenplays/shows.
Presuming the Rule of Two was abandoned or abolished, what would a return to the old Sith ways - a time when Sith numbered in the thousands across the galaxy - look like in the contemporary era?