As per mysterious Facebook post by the directors Anthony and Joe Russo via Facebook, it mentions the “Beginning the end” which marks the Avengers 4 officially starting to film and the “beginning of the end” for the ten-year story arc in the Marvel Universe. Also noted was that Spider-Man will show in Avengers 4 in some form and that the Spider-Man Homecoming sequel will be the start of the Marvel Universe’s fourth phase which is said to be “very, very, different” from what we have seen already in the Marvel Universe.
So far, we know that the Avengers 4 is due out in theatres on May 3, 2019, which follows the story from Avengers 3 Infinity War which will be coming to theaters on May 4, 2018.
About Avengers 3 Infinity War
Avengers: Infinity War is an upcoming American superhero film based on the Marvel Comics superhero team the Avengers, produced by Marvel Studios and distributed by Walt Disney Studios Motion Pictures. It is intended to be the sequel to 2012’s Marvel’s The Avengers and 2015’s Avengers: Age of Ultron and the nineteenth film instalment in the Marvel Cinematic Universe (MCU). The film is directed by Anthony and Joe Russo, with a screenplay by Christopher Markus & Stephen McFeely, and features an ensemble cast that includes Robert Downey Jr., Josh Brolin, Mark Ruffalo, Tom Hiddleston, Chris Evans, Chris Hemsworth, Jeremy Renner, Chris Pratt, Elizabeth Olsen, Sebastian Stan, Benedict Cumberbatch, Paul Bettany, Samuel L. Jackson, Cobie Smulders, Benedict Wong, Zoe Saldana, Karen Gillan, Vin Diesel, Dave Bautista, Bradley Cooper, Pom Klementieff, Scarlett Johansson, Benicio del Toro, Tom Holland, Anthony Mackie, Chadwick Boseman, Danai Gurira, Paul Rudd, and Don Cheadle. In Avengers: Infinity War, the Avengers join forces with the Guardians of the Galaxy to confront Thanos, who is trying to amass the Infinity Stones.
The story of Avengers 3 Infinity War takes place four years after the events of Guardian of the Galaxy Vol 2 with the Avengers being torn apart after the events of Captain America Civil War and joining forces with the Guardian of the Galaxy to battle Thanos.