I'm not opposed to Sabellian, either; I think his character in TBC is great - and regardless of his ultimate role in Dragonflight it'll be nice to see him snark his way through a good quest-chain or two. I think it'll also be nice to give Wrathion a real challenge in the form of one of his Black dragon peers, especially since he more or less steamrolled over most of the others when he was solidifying his grasp on power and building the Fangs of the Father to attempt to slay Deathwing. I'm hoping that if Sabellian does turn out to be evil and/or still corrupted, he puts up a better fight than Fahrad, Nalice, or Hiram Creed.