I don’t know exactly how they will portray Ben’s redemption, but I definitely see it happening, and I think Rey will play a part of it. I think it will be romantic love that puts the galaxy back together.
It’s a theory I’ve heard often (even literally my mom said this was her theory after she saw TLJ) and while I don’t have anything against it, personally I’d be surprised if it happens in an explicit “Rey and Ben are a romantic pair and will live happily ever after” way.
I doubt it will happen. Other than that scene where Rey and Kylo touch hands, the rest of the sequel trilogy seems weirdly asexual to me, at least in the traditional sense. Like it’s something that purposely being tiptoed around.