Marvel Cinematic Universe fans are busy combing through all the fine details of the first Avengers: Endgame trailer looking for more clues to how the Infinity War sequel's storyline will play out. That search has included trying to dig up the Marvel Comics Easter eggs that are typically included in any new MCU movie footage - and that early search has turned up a pretty somber reference to the original "Infinity Gauntlet" storyline that started it all:
As you can see, this Avengers: Endgame scene of Bruce Banner and the Avengers trying to tally which heroes of the MCU are either confirmed dead or missing is a direct reference to the original "Infinity Gauntlet" comic, which has a detailed panel of every Marvel Comics hero that was lost when Thanos wipes out half of all life in the universe. Obviously the list of MCU victims will be different, but fans are already going in on additions like Daredevil and Luke Cage being included in the comic book art, since both heroes recently had their MCU Netflix series abruptly canceled. Ouch.
In the comics, Thanos' infamous "Snap" is actually the very beginning of the story, as the Marvel Comics heroes are largely unaware of the threat of the Infinity Gauntlet and its six gems until after it's already too late. What happens after the panel above is that powerful factions throughout the galaxy begin to search for the source of the devastation, while Earth's heroes mount a desperate attempt to attack Thanos' stronghold head-on. In addition to the heroes, the cosmic entities of the universe (Eternity, The Living Tribunal, etc.) hold their own court to determine if they must intervene against Thanos' disruption of the natural order. Those entities then mount their own attack against Thanos in concert with Earth's champions - which could be a major part of Avengers: Endgame that we have yet to see. Entities like Eternity have been teased as part of Ant-Man's Quantum Realm, which will clearly have a big role to play in Endgame. It's also been teased that Thanos may not be the biggest threat in the film, which would certainly be true of the Marvel cosmic entities decide that mortals have obtained a power they should not hold, and take drastic action to strip that power away.
Avengers: Infinity War is now available on home media. Upcoming Marvel Cinematic Universemovies include Captain Marvel on March 8, 2019, Avengers: Endgame on April 26, 2019, and Spider-Man: Far From Home on July 5, 2019.