So what happened to the fallen?
If they're not dead, where did the vaporised superheroes go? The internet seems convinced that they're well alive but in an alternate universe.
According to Reddit user Enervata, Thanos may not have extinguished half the universe. Instead, he created another universe where Spider-Man, Black Panther, and the other supposedly disappeared get transferred to. (And in their universe, it's the other Avengers who are goners!) One possible outcome in Endgame is that those who "survived" the snap may sacrifice themselves to save the other universe. Or, in a drastic turn of events, the two universes may stay split.
Reddit user joethehamface speculates that the Quantum Realm, where Scott Lang gets stuck for a while, could be the bridge between these alternative universes. This would definitely explain why everyone in the Endgame trailer puts on Ant-Man suits. Hopefully, we'll get see most of the Avengers, including those who disappeared in Infinity War, make it out of the new movie alive!