That's really the only sort of satisfying culmination this can come to. If he returns as simply another bad guy that will be pathetic, since he had much more firepower in the past and still couldn't beat the prison group, so it will just be retreading old ground, only in a lamer fashion.

If they manage to make it so that the two groups have to join forces though, and do it in a way that is natural and not contrived (a tall and likely impossible order), I think that would justify the arc.

And btw, I still haven't seen the episode. I'll catch up once the new one comes out this Sunday.