Marvel's Phase 3 kicks off with Captain America: Civil War this May and wraps up with Avengers: Infinity War - Part II and Inhumans in 2019. While we're still at least a couple of years away from the Phase 4 slate being announced then, there's already a lot of speculation online about where Marvel boss Kevin Feige will take things next once Earth's Mightiest Heroes finally come face to face with Thanos. With so many new characters being introduced over the next few years and almost countless rumours in regards to certain stories and moments from the comic books being recreated on the big screen, it's surprisingly easy to look at what we know (or at least think we know; if nothing else, Marvel are never short on surprises) to come up with some pretty convincing theories about what the future holds for these characters. From adaptations of huge moments and storylines to surprise cameos and crossovers, Phase 4 needs to be a game changer if Marvel hopes to remain on top and avoid both so-called "superhero fatigue" and the competition they'll soon face from the DC Films Universe. If only one of these theories ends up panning out, they'll have succeeded, but whether or not they'll have the guts to take such risks is hard to say...