Entertainment Weekly.com has posted an article by Anthony Breznican that announced that Leonard Nimoy has joined the cast of Transformers Dark of the Moon and will voice Sentinel Prime.
"Mr. Spock himself, Leonard Nimoy, has joined the film as the voice of Sentinel Prime, the predecessor of Optimus Prime whose wrecked body is seen in the teaser trailer, found crash-landed on the moon by the Apollo 11 astronauts in 1969. Later, after being brought to earth, he takes the disguise form of a fire engine in the movie’s massive, climactic battle through Chicago.
Apart from his obvious Star Trek cred, Nimoy also has a history with Hasbro’s shape-shifting alien robots: He was the voice of Galvatron in 1986?s TheTransformers: The Movie.
Transformers filmmaker Michael Bay had toyed with the idea of inviting him to play a voice in the second movie, Revenge of the Fallen,
but wasn’t sure he could pay the veteran actor enough. “I was too
scared to ask him,” the director says. “Plus, he’s married to Susan Bay,
who’s a cousin of mine. So I had to be careful. I’ve met him at family
functions. But he told me, ‘I would be honored. I’m glad to be back!’”"