*bites down on knuckle* Noooo! Not you too, milady Nelliel! Where is this idiocy coming from? Perhaps Grimmjow is contagious? *bursts out laughing* Because an Arrancar's Hierro can take it, doing it to your mate would be awful form, and the suffering is expected for the Plucky Comic Relief. Thank you, milord Ulquiorra; thank you! *shakes head* Ah, milord Ulquiorra! The one time you don't spew manure, they take your words as bad as if you had.
I heard a little bird say Kubo was going to dedicate Ichigo-isn't-the-main-character-for-once time to that end. However, consider that this little bird also said Kubo couldn't think of a reason to bring Hallibel back because she had no incentive to leave Hueco Mundo...only for her to be the second Arrancar brought back into the story....I tend to think that little bird is essentially full of shit and it'll probably never happen.
Haha technically, Halibel didn't have a reason to leave Hueco Mundo...he just forgot to mention she was chained up in a dungeon somewhere. Just by what he said most everyone assumed the new arc (the ice castle) wouldn't center back into Hueco Mundo and therefore she may not have an appearance at all. I think her appearance flowed alright, since Kubo seems to be more plot-oriented. I would really love to see more character development though, so I wouldnt count on seeing a lot more on anyone's backstory, main character or not. >.>