Following the Super Bowl trailer, the official synopsis for The Avengers: Endgame has been revealed through Disney sites.
The Australian Disney website has it as:
After the devastating events of Avengers: Infinity War (2018), the universe is in ruins due to the efforts of the Mad Titan, Thanos. With the help of remaining allies, the Avengers must assemble once more in order to undo Thanos' actions and restore order to the universe once and for all, no matter what consequences may be in store.
Watch the two promo trailers above; here is the first official image of Robert Downey Jr., poster and title. The Avengers: Endgame has an April 26, 2019 release directed by Joe and Anthony Russo also starring Chris Evans, Scarlett Johansson, Chris Hemsworth, Paul Rudd, Karen Gillan, Jeremy Renner, Don Cheadle and Bradley Cooper.