When we first heard of Marvel's Grand Plan, which spans solo hero movies and the respective Avengers films, the natural assumption was that the final of the Avengers movies will be a conclusion.
As it turns out, this isn't necessarily the case. If anything, it will end something and begin another—as to what these will be, the creators are not yet revealing anything.
Speaking to IGN, Joe and Anthony Russo, who were responsible for Captain America: The Winter Soldier and the ultimately cool Captain America: Civil War and are set to direct Avengers: Infinity War, stated that the two Avengers films will play several roles the Marvel Cinematic Universe.
In the same way that recent solo Marvel films have been setting up and expanding storylines by seeing cameos and interwoven stories, Avengers: Infinity War and its untitled sequel will also provide the same treatment.
"I can't get into too much detail about who we're introducing, but these two movies are intended to be the culmination of everything that has happened in the MCU since the very first Iron Man movie. In being a culmination, these movies are in some ways going to be an end to certain things, and in some ways, they're going to be the beginning of certain things."
Without going into the specifics of who may be in the next movies or where it will go from there, the Russo brothers did hint that, when it comes to deciding the kind of character and stories to tell, the process is influenced by both preference and story logic.
Avengers: Infinity War will premiere in 2018.