TCTTS said:
Let's talk Anakin/Vader. How, exactly, would he come back and for what purpose? I absolutely want to see it, but I can't envision how or why. To talk Kylo away from the Dark Side? If so, why wouldn't he have done that by now?
I think we might need to clarify what we mean by "come back." I think it's VERY likely that we're going to get some kind of backstory on Anakin that helps inform the present, and that we might see him through some kind of flashback. So that would be Hayden Christensen making an appearance possibly, but not being back in the sense that he's affecting current events.
I think that scenario is more likely than having a force ghost Anakin that's doing something in the present.
But that said, I do think him impacting the present is possible, so let's do some wild speculating.
The simplest is what you said, to talk Kylo back from the edge. There could be a lot of workarounds for 'why wouldn't he have done that by now.' Perhaps while Snoke was alive he was 'blocking' Kylo from communicating with him somehow. Or that Kylo hadn't progressed to the point where he could reach him but something that happens in this movie allows him to do so.
There hasn't been much established at all on how exactly the force ghosts work, so there's a lot of room there for Abrams to just make something up.
Or maybe it's Rey that he reaches out to because he can still feel that Kylo can be redeemed so he talks her into trying again? That would be weird probably... but possible I guess. I kind of find it unlikely that he'll speak much...