For now lets take a look at who the cast members will be
Humans
Johnny Whitworth (as the main human protagonist)

Emmanuelle Chriqui (girlfriend of the main human protagonist)

Tyrese Gibson to reprise his role as Robert Epps

Ray Park

Scarlett Johansson

Jeremy Renner

Christian Bale

Anne Hathaway

Timothy Olyphant

Paula Patton

Tom Hardy

Joseph Gordon Levitt

Bruce Willis

Ben Kingsley

Next up are the autobots and the people to voice them
Peter Cullen to voice Optimus Prime

Leonard Nimoy to voice Sentinel Prime

Colleen O'Shaughnessey to voice Override

Peter Renaday to voice Ultra Magnus

Brian Bloom to voice Trailbreaker

Chris Cox to voice Hound

Bumblebee

Sumalee Montano to voice Moonracer

Robert Foxworth to voice Ratchet

James Remar to voice Sideswipe

Sunstreaker

Bruce Greenwood to voice Springer

Phil LaMarr to voice Windcharger

James Avery to voice Silverbolt

James Horan to voice Fireflight

Slingshot

Skydive

Sky Shadow

Michael Clarke Duncan to voice Omega Supreme

and now for the Decepticons and for who should voice them
Lance Henriksen to voice Skyquake (the main villain)

Steve Blum to voice Blitzwing

Robin Atkin Downes to voice Cyclonus

*Kim Mai Guest to voice RatBat

Miguel Ferrer to voice Scourge

Brad Garrett to voice Octane

John DiMaggio to voice Dirge

Mark Rolston to voice Thrust

Kevin Grevioux to voice Onslaught

Swindle

Rick D. Wasserman to voice Treadshot

Nick Chinlund to voice Vortex

Fred Tatasciore to voice Blast Off

Trypticon

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