Latino Review is reporting that right now there's a strong possibility Palpatine will return...as a Sith Ghost. Who, unlike Force Ghosts thus far, can actually manipulate the physical world to some degree.
They also say he took a new apprentice before he died. Not sure I like the logic of this one, since it undercuts the whole reason for trying to make Luke the next one, but okay. Who do you think that might be? Is Carrie Fisher going to be Darth Koka-Een?
McDiarmid is easily my favorite actor in the whole saga, so on one level I'm happy. I'm just not sure it makes any narrative sense to bring him back. If this turns out to be true, is it good news, bad, or meh?