Board Thread:Questions and Answers/@comment-10797017-20130627100621/@comment-6904925-20130627145717

Ichigo and Kenpachi we already know, but other 3 I would say one would be Kisuke due to his intelligence along with the fact he has one of their medallions now and can analyses it. I don't know about Aizen because Yhwach stated he wanted him as one of their special war powers. I don't know why but i think the Soul King for some reason. Also I don't think Orihime is one, shes not the only one who is can also heal severe wounds (there's also Retsu, Hacchi, and Royal Guard who taught Retsu).

Maybe Grimmjow because he has been able to avoid the Quincies along with killing one with a letter. Like WhiteZangestu said, Haribell could have been one at first but he changed his mind, and sees Grimmjow more of a threat than Haribell.