The last trailer of Endgame has shown the new Avengers costumes for the first time. As the filtered images pointed out, the heroes have new matching armor with more than one connection to Quantum Kingdom and Ant-Man technology.
For a long time theories and rumors have ensured that the avengers will travel back in time with the intention of reversing the damage caused by Thanos. To do this, they are probably using the Quantum Kingdom now that Ant-Man has succeeded in returning. And a fan has noticed that the new suits are actually an improved version of the Scott Lang outfit.
As the picture shows, although the colors have been adjusted, the emblem of the slab and the technology of the series appear to be the same. This seems to confirm that, indeed, the Quantum Kingdom will be one of the keys to winning the second battle against Thanos.
If the theories are true, the heroes' plan would be to go back in time to some specific moments, such as the Battle of New York, to get the Gems of Infinity for the Titan and to execute the destruction.
Fortunately, this is not the last card of the Avengers, as the newly-included Captain Marvel will also participate in the fight and possibly be the only one who can tolerate Thanos.