In the end of Iron Man 3, Tony Stark undergoes surgery to get the arc reactor removed from his chest. So, in the Avengers: Age of Ultron, is he just like everyone else (e.g., Rhodey) using the suit? If that's the case, why can't Captain America, Black Widow and Hawkeye use it too?
With no arc reactor and suits left, what is next for Tony Stark? How is Iron Man 4 going to be?