"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:
Then, in a neat little bit of CYA*, they add the following:
"Remember, until confirmed by Lucasfilm this is just a rumour. They are the ONLY people who can confirm this rumour report, or any other."
The main problem with McDiarmid returning -- SPOILER ALERT -- is that Darth Vader threw him into the Death Star's reactor shaft in Return of the Jedi, presumably killing him. However, Ryan Leston over at Yahoo! Movies points towards the Expanded Universe, where Palpatine "was reborn using an ancient Sith ritual to embody clones of himself."
It also must be noted that J.J. Abrams is no stranger to flashbacks (see: Lost), so perhaps a time-jumping narrative could be a way around Palpatine's expired state.
McDiarmid isn't the first original trilogy cast member rumoured to return. Harrison Ford (Han Solo), Mark Hamill (Luke Skywalker), Carrie Fisher (Leia Solo), Billy Dee Williams (Lando Calrissian) and Anthony Daniels (C-3PO) have all been subject to casting speculation.
But, like JediNews say, until Lucasfilm confirm anything, it's probably best to file this in the same Big Stack as all those Batman casting reports.
Star Wars: Episode VII has been written by Michael Arndt (Little Miss Sunshine) and is due to begin filming in the U.K. early next year ahead of a release in 2015.
*Cover Your Arse.