Mr. Don Murhpy himself, spells out in no uncertain terms that all information below w/ respect to voice actor selection is purely a rumor. ...imdb a usually reliable source states: Release date "summer 2006" (and this is the rumor part) "CAST" in alphabetical order...
Peter Cullen .... Optimus Prime/Ironhide (voice)
Frank Welker .... Megatron/Soundwave/Laserbeak/Mirage (voice)
Too good to be true? I sure hope not!
Also be sure to check out TFormers.com report from San Diego Comicon. With news of Alternators: Jazz, (blue) Tracks, Beachcomber (blue Cliffjumper recolor!), Landfill recolor as Constructicons, and more...