With just two movies left of Phase Three, the future of the Marvel Cinematic Universe is largely a mystery. The studio is keeping its plans under wraps, largely in fear of spoiling the events of The Russo Brothers' Avengers 4. But there are a few narrative threads to pull at, which may become important when the MCU continues on in the wake of Thanos' finger snap of death.
One of the biggest question marks is the capabilities of the Quantum Realm, which is a setting largely associated with the Ant-Man franchise. The mysterious location has been teased with vast powers, and Paul Rudd's Scott Lang was left stranded there after Thanos' finger snap of death. Kevin Feige recently mentioned how the Quantum Realm has been a long time coming, saying:
At the end of Ant-Man, we followed Scott Lang into the Quantum Realm for the first time. We were beginning to peel back the onion that would later be completely peeled back in Doctor Strange as we go into the multiverse. So that was our little test into that. But now the Quantum Realm is a whole other territory that we can play with to tell our stories. This Quantum Realm is much larger than we ever imagined, and there are all sorts of adventures to be had at that level, which perhaps we will explore in another film.
Well, this is certainly intriguing. Per Kevin Feige's comments in the book Marvel Studios: The First Ten Years (via ComicBook), it looks like the Marvel Cinematic Universe is going to explore the Quantum Realm in future films. And considering the mid-credits scene of Ant-Man and The Wasp, that event will be sooner rather than later.
The Quantum Realm has been a cloud looming above both Ant-Man movies, with the blockbusters not really explaining its powers and capabilities. Scott managed to survive his first brief encounter in the first movie, with that moment playing a big part in the rescue of Janet van Dyne in Ant-Man and The Wasp. Janet was eventually brought back with mysterious powers, with little to no explanation about the Quantum Realm given in the film's third act.
Ant-Man and The Wasp's mid-credits episode helped connect it to the greater MCU, as its set the same time as Infinity War's epic Battle of Wakanda. After going to the Quantum Realm for some samples, Scott Lang was left stranded as Hope, Hank, and Janet all turned to dust as a result of Thanos' snap of death. He was last seen floating through the mysterious setting, with no hopes of help.
But the Quantum Realm has also been teased to possibly contain time traveling and/or worm holes, which may be the key to defeating Thanos. If Ant-Man can go back in time or to an alternative reality, then perhaps he can stop the Mad Titan from ever snapping his fingers. The villain almost perished multiple times during Infinity War, so the pint sized hero could be the key to saving the galaxy.