User blog comment:IamJakuhoRaikoben/Chapter 230: The Tears of Love and Life, Review./@comment-3407832-20110412235438

I think that Bluenote will be the boss of this arc (Hades should just GTFO and wait for another arc, a villain like that should not go down after one arc) and will be handled by Gildartz.

Since Erza has always fought the sub-boss in every arc (Aria, Midnight, Ikaruga,...) and is still perfectly fine now, don't get your hope up. She will probably get either Ultear or Rusty Rose.