So...Captain America has been an agent for Hydra? The worst part of this idea is the fan backlash already starting. I only have one piece of advice to people getting upset over this: let the story play out. When Bruce Wayne died, did anyone doubt he would be back? When Supes and Doomsday slugged it out, we knew it was a matter of when Superman would come back, not if. Comics has an endless supply of these examples.
Stay patient people, outrage culture is exhausting.