How difficult would it be for Galvatron to TCB now that Optimus is gone? None of the remaining autobots can face him. He can whipe them out if he wants, and also any kind of human armed force that tryes to face him. And he can do this all alone. Probably he still has some of the bots made by humans, and can call some of the "dozen" remaing cons. Who is going to stop him? Or he will go to sleep for a couple of years to save the plot?