Jedi News brings us the following:
Information passed to Team Jedi News via an unnamed source has informed us that Ian McDiarmid is set to return to the galaxy far, far away for a part in Episode VII.
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.
Remember, until confirmed by Lucasfilm this is just a rumour. They are the ONLY people who can confirm this rumour report, or any other.