2. Captain America (Bucky)
Marvel StudiosCaptain America: The Winter Soldier ended with Steve Rogers getting through to his former friend as they fought. As a result, Bucky Barnes dragged Rogers from the water and saved his life before fleeing to explore his history and find out exactly who he is. He was last seen in the post-credits scene looking more like his old self, viewing a World War II Bucky memorial exhibit at the Smithsonian Institution. Given that Chris Evans is expected to be killed off as Captain America sooner rather than later, and given that Bucky was showing signs of coming good, the Winter Soldier is likely to become a hero and the new holder of the Captain America moniker (obviously Bucky Barnes isn't a new character, but Bucky as Captain America essentially would be). If that turns out to be the case, a super soldier with a bionic arm, Captain America's iconic shield and the moral ideals of a patriotic American hero could very easily become the main man in this franchise. Fighting for what's right and doing so in the name of his deceased, heroic former best friend? Sounds like a recipe for uber-popularity and Sebastian Stan could be destined for big things as a result.