A mysterious post appeared on Reddit this weekend that gave a scene by scene description of a trailer for the upcoming Avengesr 4 film. The post spread in the same fashion that most fan-theory posts circulate, and very few people took the description too seriously. That is, until it mysteriously disappeared. Whenever a legitimate Marvel leak makes its way onto the internet, it gets scrubbed within 24 hours (take the leaked pictures of Thor and Rocket Raccoon's new costumes for example). Reddit rarely deletes posts unless they are extremely harmful or offensive, there has been a legitimate complaint filed, or if the post gives away exclusive material. Fans are praying it was the latter.
The scene by scene description may have been deleted, but nothing is ever officially gone forever on the internet. The trailer breakdown has circulated online heavily, and can be read in full here. The trailer highlights Tony Stark and Captain America reuniting in Wakanda, The Hulk training for a rematch with Thanos, Hawkeye's transformation into Ronin, and much more. Time travel appears to be at the center of the plot, with scenes featuring an old Tony Stark in the future, and a still-breathing Loki during the Battle Of New York, peppered into the details. Ant-Man finally joins the team, M'Baku has taken Black Panther's throne, and Valkryie joins Thor on his quest for revenge. At the end of the trailer, fans are blessed with the title of the movie, Avengers: Annihilation. There is also a moment where an Infinity Stone disappears from Thanos' gauntlet, tipping the Mad Titan off to a possible plot to stop his progress in another time stream.
Take everything with a grain of salt, but keep in mind, Reddit is rarely forced to delete posts of this nature.