There will probably be a bunch of random robots and machines as bosses, but what about actual characters ? Bruticus is pretty much confirmed. Also, since Shockwave is not playable in story mode, I'm pretty sure he will end up being a boss. While playing Grimlock, I guess we'll get to fight the 3 main Insecticons or maybe some giant insect robot controlled by them. As the Decepticons, I see Grimlock or other Dinobots being bosses at some point. Also wouldn't surprise me that we get to fight Metroplex as Megatron. I doubt it'll happen, but I'd really like to fight Superion. A duo of Skywarp and Thundercracker would be pretty cool too.