(Update 5/5 5 p.m. PST: Entertainment Weekly reports that Dempsey will play Megan Fox's boss in a role that is "significant to the plot." Glad we got that cleared up.)
Dempsey told reporters in Brazil that he'll play a darker character than other humans in the blockbuster franchise, and that he begins his filming his role in the Paramount sequel this summer.
Additionally, the Internet is buzzing with rumors that "Scream 3's" Jamie Kennedy has joined the cast, based on an interview he gave Arizona radio station 8KUPD, during which he revealed he "had an interesting interview with the people behind the new "Transformers" movie and I may have a role in the movie."
However, after being contacted by TheWrap, Kennedy's publicist issued this statement: "This was taken out of context from a radio interview where Jamie mentioned he had auditioned for Transformers 3 and as a huge fan of the franchise, would love to be a part of it. At this time Jamie is in no way attached to the film."
Stars Shia LaBeouf and Megan Fox are returning for the Michael Bay film, which is set for release July 1, 2011. Frances McDormand, John Malkovich and Ken Jeong were previously announced to have joined the cast, while Josh Duhamel, Tyrese Gibson, Kevin Dunn and Julie White will all reprise their respective roles.
Besides "Transformers 3," it has also been falsely rumored that Kennedy would return for Wes Craven's "Scream 4." However, screenwriter Kevin Williamson told FearNet that Kennedy's movie nerd character will live by his own rules and stay dead in the slasher sequel.
Kennedy currently stars opposite Jennifer Love Hewitt in the CBS series "The Ghost Whisperer."
Dempsey last appeared on the bigscreen in the romantic comedies "Valentine's Day" and "Made of Honor." He's attached to star in the crime comedy "Flypaper" from director Paul McGuigan ("Lucky Number Slevin") and "The Hangover" writers Jon Lucas and Scott Moore.