Mark Wahlberg (The Departed) and his The Italian Job cohort, rising action star Jason Statham (also in War, The Transporter films). I haven't heard much else, and found out about this in a recent Entertainment Weekly interview with Statham.
If it tuns out to be true, this sounds like some pretty cool casting.
I don't doubt that both actors have at least been approached. Unlike Transformers, this movie is more about the flesh-and-blood characters (and hopefully awesome action), so casting is important on this one.
Source: Entertainment Weekly