Ben the Ren will have an arc of redemption I'm sure. I could definitely see Ford coming back for visions or some nonsense.
I don't see how you can be redeemed from killing your old, defenseless dad though. That's unforgivable in my book, there's no reason in it. If Leia forgives that and still wants "muh boy", well then I don't know what to say. That's not even taking into account all those innocent students he offed in addition to his own dad, but then again, Anakin killed a bunch of kids, betrayed his peers and choked out his wife and got to be Force Ghost and a glorified diety, so maybe Ren has the right idea.