Avenger endgame Comes with a possible time travel theory

The most awaited trailer of the year is out.Everyone was hoping it would be the captain marvel savior from the sky. But we see here a new concept that Scott Lang aka Antman shows at the Avengers headquater door. Captain America assumes that he's dead as he's "missing" in the avenger indexing of "Decimation victim"but there is scott, goofy as always hoping to talk to cap and widow about something.

How did he survive?
 The antman and the wasp ending scene found scott stranded in Quantum realm after the snap turned Hope and mr and mrs pym into dust.Either he was not one of the randomly selected victims by the Thanos or chilling at the microscopic level with a bunch of tardigrades insulated him
from the infinity stone power.

Possible concept of Avengers Endgame
During the filming of Avengers Endgame,photographers caught the cast in costumes that includes aged up Tony stark, indicating jump in time.While Infinity war recreated a portion of the big set-piece screen from 2012's Avenger,the fact that time travel is in the air lends credence to the idea that Scott or perhaps the entire crew could be travelling from timeline blip in search of opportunity to bust up Thanos.Rumors that Marvel have cast an older Cassie Lang,Scott young daughter in the movie, for Endgame only add to the speculation.