Warning: Spoilers for Ant-Man & The Wasp ahead.
Ant-Man & The Wasp may be mostly a standalone movie with a self-contained story, but the film nevertheless included several plot points building towards Avengers 4. With the Ant-Man sequel officially in theaters, Marvel Studios' 2018 is finally finished - but that doesn't mean that fans will have a shortage of topics to talk about for the rest of year as they wait for Captain Marvel.
Indeed, Marvel Studios intentionally picked Ant-Man & The Wasp and Captain Marvel as their buffer films between Avengers: Infinity War and its still-untitled sequel. Timeline-wise, both projects are set before the events of Avengers 3. This means the shocking events of Infinity War's ending don't have to be directly addressed, but also allow the pair to set up what's coming in Avengers 4.
Ant-Man & The Wasp actually takes place around the same time as Avengers: Infinity War, meaning that it's a lot more involved with Thanos' attack on Earth than it might at first seem. Here are all the ways Ant-Man 2 connects to Avengers 4, and its significance to the MCU's overall ongoing narrative.
We Already Knew Team Ant-Man Has A Big Part In Avengers 4
Even before Ant-Man & The Wasp brought the Pyms back together, we knew that Hank, Janet, Hope and Scott would be back in Avengers 4. Set photos had Paul Rudd in a recreation of the Battle of New York from The Avengers, suggesting he'll be involved in the movie's time travel plot, while leaked Avengers 4 art has since shown him alongside the survivors of Thanos' snap (and Captain Marvel), meaning he's joining the main roster of Earth's Mightiest Heroes for the film.
Meanwhile, a slip-up from Sebastian Stan, who plays Bucky, revealed that he will share the screen with Michael Douglas and Michelle Pfeiffer in Avengers 4. The same is true of Evangeline Lilly, who has likewise hinted at her role in the film. While the nature of their appearance isn't clear (and, as we'll see shortly, is even more complicated after Ant-Man & The Wasp), this means there's going to be a proper reunion.
Finally, an older Cassie Lang, Scott's daughter, has been cast for Avengers 4, hinting both at a time jump and opening up the possibility of her taking on the Stature mantle. Now the sequel's arrived, however, there's a lot more to explore.
Ant-Man & The Wasp Shows What The World Looks Like Post-Snap
The filmmakers behind Ant-Man & The Wasp have reiterated time and time again that fans should stick around for the film's two post-credits scenes. Of course, people normally stay for Marvel's traditional stinger anyway, but this latest pair were particularly important in regard to Avengers 4.
Even the jokey end-credit scene, featuring the giant ant playing the drums, offered up something important: a glimpse at a post-Infinity War world. Marvel has been delaying in addressing the aftermath, with recent MCU TV shows set before the galactic genocide. It's important to remember that after Thanos' snap, there wasn't any establishment whatsoever of its repercussions; people just started turning into dust and the movie ended. Now, we have a sense of what the purge left behind; streets are suddenly eerily quiet but for emergency broadcasts.
Scott Trapped In The Quantum Realm Leads Directly To Avengers 4
However, it's the mid-credit scene that has the big connection to Avengers 4. As Hank, Janet, Hope oversaw Scott's travel to the Quantum Realm via the Quantum Tunnel, Thanos' snapped his finger, resulting in the Pyms disintegrating into dust while a clueless Scott is trapped in the alternate dimension. This confirms where Ant-Man 2 comes in the timeline, but also serves as the most overt setup for Avengers 4 we've yet got.
The key is Scott's predicament. Without anyone operating the Quantum Tunnel, it's currently unclear how Scott will be able to come out of the microverse. There's the outside chance someone who knows how to use the tech like Ghost or Bill Foster (granted that they didn't turn to dust as well) comes to save him, but otherwise he'll be stranded down there for the foreseeable future.
As for how he'll get out, there are two options. Considering that the next MCU entry will also tackle the alternate dimension, it's definitely possible that Captain Marvel is also in the Quantum Realm (and not in space as popular theories suggest). As Nick Fury sent Captain Marvel the distress signal at the same time that the Pyms were vaporized and Scott was trapped, it's possible that in her exit she will come across Ant-Man and bring him with her on the quest against Thanos.
The other outcome is that Scott does it on his own. After all, he's escaped the Quantum Realm once before in the original Ant-Man, and were he to somehow run afoul of one of the time vortexes Janet warned him about, he would be in the prime position to provide the Avengers with the knowledge of time travel, thus starting their offensive to undo Thanos' attack. This would explain the prominence of the Quantum Tunnel in Ant-Man & the Wasp: it established that it was possible to travel to the alternate dimension without needing to go subatomic or risk being trapped.
Whichever way Scott escapes (and how Janet, Hope and Hank are brought back) will be revealed in Avengers 4 next May.