Like most aspects of the MCU, even the trailer release date for Avengers 4 is up for speculations right now. Many theories suggest that the trailer could arrive before the end of November, or November 28, to be exact.
According to We Got This Covered, a special Infinity War screening is being organised by Collider, and the growing rumours suggest that it’s being held in conjunction with the trailer release. The screening has been set for November 28( and will be accompanied by a Q&A session by directors Anthony and Joe Russo.
OK, here we go, 3 quick questions, answers direct from Kevin Feige's mouth
1) AVENGERS 4 trailer "before the end of the year"
2) Namor COULD make an appearance, still deciding IF & when
3) GUARDIANS 3 status "on hold"
— ???? (@ErickWeber) 26 October 2018
Interestingly, the trailer for Infinity war also released around the same time, ie. November 27. While Marvel is yet to make an official announcement, Kevin Feige had revealed that the trailer will release before the end of the year.
The trailer will also supposedly end the mystery around the film’s title. So far, the most popular titles surfacing the internet are Avengers: Annihilation and Avengers: End Game.
Avengers 4 will release on May 3, 2019.