I honestly cannot foresee Megatron coming back as a Stealth Bomber for the simple fact that the Decepticons already have way too much air support with Starscream an F22 Raptor, and now apparently a SR-71 Blackbird rumored to be Skyfire.
Brawl was already the military tank, and well.... we seen how easily defeated he was. lol And he most definitely couldn't be a Hummer, because GM vehicles are only sadly used for the Autobots unfortunately. lol
Honestly if they do infact bring Megatron back, which I'm almost 99.9% sure they will, he needs to be something big, mean, and most definitely very powerful.... and hopefully renamed Galvatron.