I think what will happen (in this, my favourite Ultimate title, nay, perhaps my favourite super-hero book ever - man, waiting for Ultimates 2 was like waiting for Return of the King) is this (only further reinforced by the title "Grand Theft America" which I didn't know about):
I think Captain America is a good man. He believes in freedom and the protection of innocents, and he doesn't mind killing those tyrants. But I think, in his stark morality, that these continuous preemptive strikes Fury has them doing, and the continous acquisition of power SHIELD is using to control people, as well as the superheroes becoming super soldiers as Banner, Pym, Thor, and maybe even Wasp will be replaced by Sgt Blammo and maybe even US Agent, has him worried. I think the second arc will involve Captain America using the Ultimates to take down SHIELD.
What will happen is the rest of the world will become terrified of the US' use of the Ultimates and its this that will result in Captain America realising that America is causing the problems its trying to solve.
So he'll realise that America is and has been under the influence of a controlling shadow conspiracy, that America was stolen long ago, and he'll try to take it back.
Maybe Ultron will be repsonsible in someway - if he leaked Banner, maybe he leaked the super soldier information to other countries which is why they've slowly been able to create their own super soldiers.
Maybe the details aren't right, but I'm convinced Grand Theft America is The Ultimates versus SHIELD.