Looking over some info on wookieepedia I'm beginning to think that Lucien will be Nihilus.
But then again we could be wrong on both accounts. In Star Wars: The Ultimate Visual Guide, it states that Darth Sion was the apprentice of Darth Nihilus. If this is true then Nihilus must already exist and taught Haazen the ways of the sith, dubbing him Darth Sion.
I QUIT LF!