From website Latino Review's sources comes some pretty significant and convincing theories about events that are to behold in the Marvel Cinematic Universe, especially in terms of what is to come with the current members of "The Avengers". I've also thrown some of my own theories into the mix, based on what we've heard from Marvel executives (especially Kevin Feige) and how closely/presumably close they are going to adhere to the source material. My own presumptions are also based on things that have been set up in films already released (ending with Captain America: Winter Soldier and Guardians of the Galaxy).
First, here is the order of the upcoming films on slate from the MCU:
May 1, 2015 - Avengers: Age of Ultron
July 17, 2015 - Ant-Man
May 6, 2016 - Captain America: Civil War
November 4, 2016 - Doctor Strange
May 5, 2017 - Guardians of the Galaxy 2
July 28, 2017 - Thor: Ragnarok
November 3, 2017 - Black Panther
May 4, 2018 - Avengers: Infinity War, Part I
July 6, 2018 - Captain Marvel
November 2, 2018 - Inhumans
May 3, 2019 - Avengers: Infinity War, Part II
So there it is, the final lineup of the films that will continue and conclude with a final "Avengers" team-up film. What is interesting, though, are the rumors about the events that will lead to one final, ultimate mash-up of characters.
1) This year's Age of Ultron will introduce us to some new characters (Quicksilver, Scarlet Witch, and The Vision are the three we know about), presumably with an after-credits sequence that will show us/hint to us the other characters or crossovers that will take place.
2) The first crossover being The Hulk in the Guardians of the Galaxy universe. In the comics, the Hulk is at one point sent to space (Cosmic Cube reference from the films, perhaps) and one could imagine him becoming a part of Guardians of the Galaxy 2.
3) Second crossover that we already know is planned is Tony Stark/Iron Man in Captain America: Civil War. The events that lead to this "Civil War" are actually pretty significant to the storyline of the video game "Marvel: Ultimate Alliance 2" that was released in 2009, which was based on the "Civil War" crossover comic book from 2006. In it, Captain America and Iron Man are at odds with the Suphero Registration Act, which would in term give the government a way to "police" superheroes. This Act is strongly opposed by Steve Rogers/Captain America, but supported by Tony Stark. How the movie handles the angle is up to debate, but it is rumored that Stark will in fact be more the main antagonist to the more freedom-and-liberty swaying Captain America.
4) Captain America: Civil War will apparently conclude with one of the biggest shocks in the entire series, with the death/assassination of Captain America. At the end of Winter Soldier, we are already hinted at the birth of villain Crossbones (played by Frank Grillo), the character who in the comics pulls the trigger. In the comics, Red Skull was the one that gave the order, so perhaps the same situation that results in the Hulk being sent to space can also be a similar event that, perhaps, returns Red Skull into the mix?
5) After the conclusion of Civil War, the future of Tony Stark will also be in debate, as both major leader characters from The Avengers Initiative are in question.
6) An introduction to Doctor Stephen Strange could be in order as a potential after-credits scene to Civil War in an attempt to make him the possible leader of the Avengers, especially considering that:
7) ...Thor: Ragnarok will conclude with Thor being held captive in a "galactic prison" and unable to return to the Avengers on Earth. The title Ragnarok also hints at the Norse mythology, or the "twilight of the gods" - a hint that many Asgardian characters are going to die. This film, as noted by website source denofgeek.us, will also hold some pretty significant moments that will shape the future of the Avengers. Sourcing another comic series Avengers: Disassembled, this film will be the marking point for the current member-less team of Avengers.
8) Also on the possible-leader scale is Black Panther, a character whose solo film will probably have other MCU characters involved (especially Doctor Strange, considering the introduction to the Astral Plane and how both he and Panther are closely involved).
9) All the events will lead into the first part of the Infinity War, in which both Captain America (dead) and Thor (imprisoned) will NOT BE IN IT. BUT....
10) With the recent Sony deal with Marvel having (presumably) gone through, Avengers: Infinity War Part I WILL include the introduction of SPIDER-MAN into the mix. FINALLY! The sad part is he probably WON'T be in Civil War, despite the fact he was the main superhero who was torn between Stark's and Rogers' sides in the matter. His inclusion would have made for a good tug-of-war battle, with him being the mind of in-between reason.
And here's the holy mother of God moment that, if it plays out well over the next four years, will be pants-shittingly, heart-attack inducing awesome:
11) Infinity War Part I will not have ANY of the original Avengers cast members, and will only include some of or all of the new characters because -
- they want to have the original heroes return in Infinity War Part 2 in what will be a smorgasbord of heroes beating the shit out of Thanos (holder of the all-powerful, universe controlling Infinity Gauntlet) and his goons.
In Part I, expect to see (all potentially, but VERY possibly) some of the Guardians, Captain Marvel and the Inhumans introduced, Ant-Man, Wasp, Black Panther, Quicksilver, Scarlet Witch, Vision, Luke Cage, Daredevil, Iron Fist, possibly a Bucky Barnes in Captain America outfit (as was in the comic books - yes, the Winter Soldier takes on the mantle of Captain America at one point), SPIDER-MAN, and Doctor Strange.
A couple years later, in the conclusion of the Infinity War with Part II, Iron Man, Thor, Hulk and STEVE ROGERS HIMSELF (not dead, anymore, somehow) will return to kick ass with all the new Avengers to defeat Thanos and put the world at ease.
And thus will be the strong possibilities on how the MCU will end, in one of the greatest, most expertly-planned cinematic undertakings in film history. Seriously, the planning involved from 2008's Iron Man to 2019s Avengers: Infinity War Part 2 to connect all the characters and lead to an ultimate finale is more mind-blowing than what the writers for the television mind-fuck Lost had to go through on a season-to-season basis.
In summary, expect the events of Civil War, Thor: Ragnarok, and Infinity War Part I to make for some rather dark entries in the series. Doctor Strange will lighten the mood and introduce us to another level of existence in the Marvel universe with the Astral Plane, which will connect to Black Panther and the solo films for Captain Marvel and the Inhumans, but expect the conclusive film, Infinity War Part 2 to be everything a Marvel comic fan AND fans of the films have been waiting for, drooling for, pining for, and getting geek boners for. There's also that neat possibility that with the space adventures of Guardians of the Galaxy 2 that we are introduced to even MORE of our favorite smaller, lesser-known characters from the Marvel universe.
If this all plays out, even if all these rumors become 100% true and this news truly has spoiled everything for those who have read this, it will still be a marvel to experience.