User blog comment:Mlgrsd/Will we see Michael in the season finale?/@comment-25529244-20170428175915

If he comes back (I doubt it'll be the S12 finale though) then I think he'll have a personal hatred against Sam and Dean for locking him up in the first place. As for role, I think he'll either be a main villain/psychopath bent on destruction/gone insane from being trapped in the cage, or start off as against the Winchesters but then allies with them later on.