The trailers for the trailers may only show footage from the first 15-20 minutes of the film. Compounding that is the fact that Marvel is notorious for making digital alterations in order to hide plot points, meaning scenes from the trailers may play out very differently in the film.
There's already substantial evidence Marvel has taken this approach with Avengers: Endgame. One scene from the trailers, for example, shows a group of Avengers staring up at the sky; there's a clear gap, suggesting another person - most likely Captain Marvel - has been carefully edited out. There'd been speculation that another scene had been similarly edited, one in which Hawkeye raced through tunnels with an explosion behind him. It clearly showed a combat scene, and yet there was no hint of who he was fighting.
Related: Avengers: Endgame Story Timeline & Trailer Scenes In Order
One eagle-eyed Thanos' Outriders, and that the explosion was a way of dealing with a group of them.
This revelation makes the scene far more intriguing. Hawkeye has assumed the Ronin identity in Avengers: Endgame, a dark vigilante persona he adopted in the comics at the darkest points in his life. He's headed to Japan, and Black Widow tracks him down in order to persuade him to return to the Avengers Compound and the team in a last-ditch desperate attempt to defeat Thanos. It had originally been assumed that the explosion was an action scene in Japan, with Clint perhaps taking down a group of Yakuza thugs.
The 3D trailer, however, makes it clear that Hawkeye is taking on the Outriders. This is possibly from the Thanos' "retirement plan" to the Avengers, and that they'll head out into space to confront the Mad Titan.
Either way, it's clear that Thanos and his forces are far from retired and, at the very least, Clint Barton will get to enact some form of revenge on them in Avengers: Endgame.
