Ack, I don't do dead people.
Sorry to disappoint you, though!
He's just a new Sith Lord. I think the galaxy is big enough that you can have more than one Sith Lord. Nihilis and Sion co-existed but didn't work together. To be _The_ Dark Lord of the Sith, you have to be someone like Palpatine, and that was a little (a lot) too big of a theme for me to want to tackle.