(SPOILER)Bagamnan eventually gets bested, yes, but he by no means reforms his behavior. He is last seen getting thrown off a bridge and towards the waiting jaws of some predatory creatures. Revenant Wings shows that he apparently survived, but he is still, to the very core, a conniving, bloodthirsty bastard.

But yes, we could still get to control a bangaa. Just, by all rights, not that particular one.