I'm not sure I will find it satisfying if, after he loses or gives up in IX, he is put on trial or has to do some kind of penance dictated by the Resistance. I think his repentance/comeuppance (if any), should come from himself, not artificially handed out by a (questionable?) new governing body.

On the other hand, I've seen speculation that he will turn out to be a fairly competent leader in what he dictates, but I'm not sure he is grounded enough for a political position.

I think he will be deposed by Hux and will escape, and will become disillusioned with his vision for the Galaxy. If this happens, he could ally himself with Rey briefly to bring the FO down, but not permanently.