I think Lucien Draay will go off and do something else. After this last little fight with Haazen, I think Draay, though blinded, has returned to the light. He has been through so much, he probably would rather fade into obscurity and get lost. To live with the attrocitites he comitted. He could not become Darth Sion, read on and you will see why I believe this.
Also I have my doubts about Haazen coming back from the dead, and becoming darth sion. Admit it, everyone knows where this is going.
In case you do not believe me: http://starwars.wikia.com/wiki/Darth_Sion
Originally Posted by wikipedia's page on darth sion
Darth Sion, the Lord of Pain, was a Sith Lord who lived in the time of the Old Sith Wars. As a Sith Marauder in the Great Sith War, Sion fought for Exar Kun's Sith Empire until the day he was struck down. Rather than die, though, Sion found that by calling on his pain, anger, and hatred, he could rise from certain death and achieve immortality, at the cost of all-consuming agony. With a body fractured and decomposing, but held together by the dark side of the Force, Sion survived the Great Sith War.
Sion has been around a lot longer than Draay.
Haazen survived explosives--he was young when it happened, too. It is a possiblity.
Still there is a big difference between surviving explosions, and hanging on for life with the dark side of the force from having been struck down. Struck down implies from a lightsaber it would seem since SW:ANH first hit theaters.
Furthermore if you look at Sion and Haazen side by side, you'll notice that sion still has his shoulder (at least) still available and intact (more or less as opposed to replaced with prosthetics) on his right side--if not the whole arm. Whereas Haazen's right arm up to and including his entire shoulder was all mechanical.
Reference for haazen: Comic, Knights of the old republic #34 Master vs Padawan, page 10. You will see it.
Since wikipedia editors seem to be slanting it trying to make haazen look as close to sion as possible, I feel it necessary to point this out.