The other major superhero being introduced in Captain America: Civil War is Black Panther. Ruler of the African nation Wakanda, the first black superhero is set to play a major part in the MCU going forward, with Chadwick Boseman signing a five-picture deal. While he's already getting a pre-standalone appearance (he gets his own movie in 2017) in Civil War, Marvel could use the presence of his home country in Age Of Ultron as an opportunity to introduce him ahead of that. He's certainly more likely than Spider-Man. Unlike the biggest mainstream superhero on the planet, few people are aware of Black Panther, making a bit of carefully cultivated hype all but necessary. And with Boseman already cast as T'Challa it'd be easy to shoot a quick scene in costume without raising many mole eyebrows. This does depend somewhat on how much of Wakanda and its people are seen in Age Of Ultron - it's confirmed the team will visit there, but whether they'll meet the royalty is unclear. If T'Challa isn't in the movie proper, a scene of him assessing the damage they no doubt wreak would seem fitting, setting up him travelling to America for Civil War. Likelihood: 6/10