Why was the ending to the Arrancar arc so brief?
I think the whole thing will be explained in the manga. I haven't caught up yet completely but last I saw


   it looked like stuff's gonna go down with the soul king so I expect they'll explain more regarding that.Also at the start of the current arc they briefly showed Aizen being locked away almost as if they were hinting you should keep him in mind. I think it's gonna go deeper.