https://www.cnet.com/news/how-avengers-4-trailer-captures-a-history-of-cinematic-hype/

Complicated theories about a trailer-release date for the film have arisen based on past practices, planned events and possibly the waxing and waning of the moon.

Trailer watchers have been burned before. Fans hoped Wednesday, Nov. 28 would be the big day. It was almost a year after the Avengers: Infinity War trailer came out, and the film's directors, brothers Joe and Anthony Russo, were speaking that night in Hollywood at a screening of Infinity War sponsored by Collider.