It was pretty obvious that Netflix was planning something big when it released Daredevil Season 1 last year, and there was a bigger plan to create a universe of superheroes within the Marvel Cinematic Universe that had already been very well established in the Avengers related movies (Thor, Captain America, Iron Man, etc.) as well as the ABC shows (Marvel's Agents of S.H.I.E.L.D. and Agent Carter). Daredevil began this darker foray into Marvel, followed by the equally successful Jessica Jones. Coming up in 2016 will be Luke Cage and possibly Iron Fist, and then grouping all four Netflix Marvel stars into The Defenders. So how will this Defenders Universe alter the Marvel Cinematic Universe?
If Marvel is smart, and it has demonstrated a long-term plan for all of these characters, then it knows how to tie its shows together. In Daredevil Season 1, several references were made to the Avengers, and the reason why the villain Wilson Fisk (Vincent D'Onofrio) was trying to clean up Hell's Kitchen was related to events at the end of the Avengers when New York was attacked. However, much of the tension on Daredevil was related to Matt Murdock (Daredevil's real name, played by Charlie Cox) dealing with Fisk and fully becoming the costumed super-hero.
Then Jessica Jones happened, and it also introduced us to a world where superheroes exist, as many who encounter Jessica (Krysten Ritter) are not surprised by her augmented strength. Also thrown into this mix was a villain named Kilgrave (David Tennant), who had the power to take over peoples' minds. This storyline was also pretty self-contained, but there was some cross-over with Daredevil as Claire Temple (aka "Night Nurse" played by Rosario Dawson) appeared on both shows.
Daredevil Season 2 will be released in March of 2016. Conflicts that Matt Murdock will face will be related to meeting other comic book sourced characters like Elektra (Elodie Yung) and the Punisher (Jon Bernthal). This could also be a self-contained story that does not involve the Avengers universe in any way.
Both first seasons of Netflix shows of Daredevil and Jessica Jones did not allude to the events that occurred in Avengers: Age of Ultron, but with the release of Captain America: Civil War, this could change.
The trailer for the film shows that Captain America will secede from this team in order to protect the Winter Soldier, and this will cause a lot of hostility between him and his teammate, Iron Man. There is reported to be a lot going on in Captain America: Civil War as practically all Avengers are going to be involved in this film somehow, with the exception of Hulk and Thor, who will have their own movie later in 2017.
In the original Marvel Comics, the Civil War was an event where the government stepped in and demanded superhero registration. Certain Marvel heroes like Iron Man were on one side supporting the legislation, while others, like Captain America, stood against it. Both parties clashed, which seems similar to the events of the movie.
It is possible that Captain America: Civil War could have some serious fallout that could affect the Netflix Defenders universe directly. Luke Cage is planning on premiering later this year, with Mike Colter reprising the role that he played in Jessica Jones. Luke Cage might have a difficult time living in a world where superheroes have fought, and he might want to consider keeping his augmented strength a secret or he could be exposed.
The biggest question mark in all of these Defenders series is not if all these darker superheroes will ever meet, because that has always been part of the plan, just a question of when. Not much is currently known about Iron Fist, or the role he will play in this very connected universe that is Marvel now.