Additionally, Ant-Man and The Wasp’s mid-credits scene revealed that Paul Rudd’s Ant-Man has been stranded in the Quantum Realm, with the mysterious setting having time traveling and/or universe traveling capabilities.
There’s a ton of possibilities, and the device seen in Avengers 4’s photo is yet another one.
With Nick Fury contacting Brie Larson’s Captain Marvel, it’s very possible the end game could involve her.
Since it seems impossible for the Marvel Cinematic Universe to continue on without the likes of heroes like Black Panther, Spider-Man, and Doctor Strange, there are a tons of theories regarding how the good guys could somehow bring back the dusted characters in Avengers 4.