We have seen many high-profile cameos in Star Wars Rebels
through three seasons. Whether it be Billy Dee Williams as Lando, James Earl Jones as Darth Vader, or even Forrest Whitaker as Saw Gerrera, the show has been able to attract these actors to reprise their roles.
Since the show takes place in the heart of the Empire's reign, it's easy to assume we could get another appearance from The Emperor in the show's fourth and final season. The character appeared as a voice in season two, and he was voiced by Sam Witwer.
If Palpatine does show up again in season four, a new rumor suggests that Ian McDiarmid could be reprising his role for the show. Star Wars News Net
says they've heard that McDiarmid has recorded lines at the same place and time that Warwick Davis did. Davis will plau Rukh in the final season, and SWNN says it's a strong possibility that McDiarmid will be playing the Emperor in animation for the first time ever.
We know Dave Filoni loves bringing back the actors who originally played the characters on screen, so it wouldn't be a surprise that he would choose McDiarmid over Witwer in this instance.
Head over to SWNN to see the full report here