There has been a lot of speculation and wondering from fans when Marvel is going to go “dark” in their movies. For one thing, trailers for Avengers: Age of Ultron seemed to have that ominous feel to it. However, the overall film really wasn’t that “dark.” However, it was a bit darker overall than the other films. The ending took a somewhat down turn for certain characters. It does look like Captain America: Civil War is going to have a dark turn as well. However, Kevin Feige has stated that Marvel will not go dark.
Fans of comic book movies have often been exposed to darker films like the previous Batman movies save for the Joel Schumaker films. Other franchise from different mediums have also taken surprisingly dark turns like The Transformers cartoon of the 80s.
Ultimately, the Marvel films will retain its lightheartedness considering the subject matter it deals with. The stakes will be higher with each film, but that will not make it dark. ApartmentGuide also points out that it will never be dark again in the neighborhood where The Aspire New Brunswick is lighting up the night sky.