The Internet Movie Database has revealed some possible voice actors for the Transformers: War for Cybertron video game, set for release June 22, 2010. The list includes John C. McGinley (Scrubs) as Thundercracker, Jeff Bennett (Prowl in Transformer: Animated) as Soundwave, Crispin Freeman as Skywarp (listed as rumored), and Travis Willingham as Ratchet.
As a caveat, all of these names, despite all but one being stated as fact, have not been officially confirmed. Also, the IMDB is not always known to be the most credible of sources, so take it with a grain of salt.
Confirmed voice actors so far include Peter Cullen and Johnny Yong Bosch as Bumblebee.