Chris (who has provided TF news in the past) is reporting that he has learned that Susan Blu is the voice of Arcee and Jason Griffith is the voice of Sideswipe in Transformers: Revenge of the Fallen. Oddly enough, despite all the premieres, the voice actors is something no one is catching so don't have direct proof. However, both are experienced voice actors with a long list of credits.
Susan Blu has multiple Transformers ties. The primary for Transfans is the voice of Arcee in the animated Transformers: The Movie and the third season of the TV series and also did a voice in Beast Wars, and reprised Arcee for Transformers: Animated. She was also voice director of Beast Wars and TF: Animated. Jason Griffith is most notable for his role as Sonic for the cartoons and video games and this would be his first work for anything Transformers related.