According to a downloaded copy of his resume, Alan Silvestri has been tapped to score Stephen Sommers' G.I. Joe. Silvestri regularly works with both Robert Zemeckis and Stephen Sommers. Previous soundtrack credits of Silvestri include the Back to The Future trilogy, Forrest Gump, The Mummy Returns and Beowulf.
From the same site, and according to his resume, Michael Giacchino is set to score the Wachowski brother's Speed Racer. Giacchino's music has previously been heard in the Pixar films The Incredibles and Ratatouille, as well as ABC's award-winning series Lost.