(Do I really need to put a spoiler tag for events from the original STAR WARS trilogy? Well just in case, this is your warning. There’s also details about the STAR WARS expanded universe, so you might want to avoid that too.)
The specifics of the role are unclear, but it seems likely that McDiarmid will be returning to his signature role of Palpatine. Whether as the original or a clone of, we are yet to discern.
I’m not that familiar with the expanded universe for STAR WARS, but apparently Jedi News is referring to when Palpatine is reborn as a clone using an ancient Sith ritual, which would explain how he survived being thrown into a reactor shaft.
In my (not so) humble opinion, this would be one of the worst choices they could make. No, really. Palpatine is dead, let him be dead. Bringing him back only serves to destroy the end of Return of the Jedi, and muddy things up a bit. If your primary evil antagonist can’t be killed, or if he is and is only resurrected, then what’s the point? The films become meaningless.
Now, with that said, if they wanted to bring McDiarmid back for flashbacks of some sort, I might be okay with that. I’m not sure who would be having flashbacks though.
The other possibility is having actual scenes taking place in history that would establish something very important, then coming back to the present and dealing with whatever it is.
This rumor stuff, and not knowing is killing me though. One thing is for sure, I don’t see a lot of potential for pleasing many of us fairly hard core Star Wars fans, I really don’t think there’s a lot they can do for us… But I guess that’s me being overly pessimistic.