Well, Marvel Studios wanted to hold one surprise back for fans just waking up in those Pacific time zones, because now we have the first official Avengers: Endgame poster, which also finally reveals the official new Avengers 4 release date of April 26, 2019!
The earlier release date seems to reflect Marvel Studios' desire to release Avengers: Endgame simultaneously on an international scale, rather than doing the staggered release that we typically see, with the UK getting new Marvel Cinematic Universe movies about a week or so earlier than the US. Obviously the idea is to cut down on potential spoilers leaking out, as it seems like Avengers: Endgame will be keeping the majority of its plot under tight wraps, to keep fans as fresh as possible, going in.
This earlier release date constitutes an exact repeat of Marvel Studios' release date change for Avengers: Infinity War, which was moved up to April 27, 2018, from its original May 4 release date. It worked (pretty) effectively: the simultaneous release in the primary international markets not only kept Marvel fans "in the know" at the same time, it also motivated a massive global audience to get into theaters as quickly as possible on opening weekend, helping to generate record box office numbers that ultimately led to a $2 billion+ box office haul.
Hopefully, the marketing for Avengers: Endgame will continue to be somewhat reserved and withholding. There really is little need to light any kind of fire under fans; most of the audience that turned out to make Infinity War a $2B success will want to show up and see how it all turns out. More so than the first film (which sported a big twist ending), this sequel will be wall-to-wall moments of juicy reveals and spoilers, once again motivating audiences to flock to theaters as quickly as possible to catch it.
In other words: better clear your schedule for that last week in April - you don't want to be late to this party.
Avengers: Infinity War is now available on home media. Upcoming Marvel Cinematic Universe movies include Captain Marvel on March 8, 2019, Avengers: Endgame on April 26, 2019, and Spider-Man: Far From Home on July 5, 2019.