User blog comment:Korbzy/Do you think that Gotei will use Aizen for fight vs. Quincys?/@comment-11051098-20130818094250

I doubt they will release him from Muken. He will likely just do whatever he wants and fight/kill Shinigami and/or Stern Ritters as he pleases. Releasing him HOPING to have him fight on their side would be a huge mistake.