It's funny to think that of all the characters in Avengers: Infinity War, the characters people are talking about the most right now are the ones who haven't been shown. There's been a LOT of talk about the distinct lack of Hawkeye in the marketing for Infinity War, and to a far lesser degree Ant-Man (and Wasp). The Russo brothers have assured us that any character that doesn't get screen time in Infinity War will get their due in Avengers 4, but the real interesting piece of information came when they took it a step farther during the set visit for Infinity War, telling CinemaBlend and other outlets,
I think from a plot standpoint, if there's any corollary, Ant-Man and the Wasp probably has some elements that stitch in.
Per Joe Russo's own words, Ant-Man and the Wasp has events that tie into Avengers: Infinity War. That's fairly significant given that the sequel takes place right between the two Avengers movies, but up until now, we haven't heard any word on how the standalone movie connected to the rest of the MCU. However, the movie is placed in a key position to do just that and it all might have to do with the Quantum Realm and the mysterious whereabouts of Captain Marvel.
The plot of Ant-Man and the Wasp has been kept mostly under wraps except for the bare bones, which features Scott Lang dragged back for one last mission with Hope van Dyne and Hank Pym. We also know that this will have to do with the Quantum Realm -- the subatomic dimension of formerly no escape -- that serves as the prison of Janet van Dyne, the original Wasp. As far as we know, the rest of the sequel will remain fairly grounded, so it stands to reason that we should single out the one cosmic portion being important to the two heavily cosmic blockbusters.
It's entirely possible Ant-Man and the Wasp could have other ties to the Avengers movies. Timeline-wise, we don't actually know when the movie is taking place, so there could be some one-the-nose references directly calling out the events of Infinity War. However, Scott Lang being under house arrest seems to imply that this is soon after the events of Captain America: Civil War, meaning there'd be no way Scott or Hope know about Thanos yet.
So, the Quantum Realm is our best guess, but how could it play into Infinity War or Avengers 4? Seeing as how no one knows anything about Avengers 4, it's impossible to say for sure, but the first thing that comes to mind is the last remaining Infinity Stone, the Soul Stone. It's possible that the stone is hidden away in the Quantum Realm. The Soul Stone hasn't been featured in any marketing material except for one poster involving Iron Man, so for all we know it might not even be in the movie, but it seems unlikely that Marvel would wait until Ant-Man and the Wasp to introduce the final stone.
This brings me to a popular fan theory that Captain Marvel is actually trapped in the Quantum Realm and is found by Ant-Man and Wasp, who then bring her to the present day MCU. How Carol Danvers ends up in the Quantum Realm is anyone's guess, but it would be one way to explain where she's been all this time if she first got her powers in the 90s. This isn't to say that she plays a big part in Ant-Man and the Wasp. I could see Scott and Hope somehow leaving the door open, so to speak, when they free Janet from the Quantum Realm, giving Carol her chance to escape. Then she pops up in Hank Pym's living room (or wherever) in a post-credits scene, which leads right into how she came into this predicament in Captain Marvel.
If this were to be the case, then that means that Scott and Hope are essentially responsible for getting Carol up to speed for Avengers 4. If that's how it plays out, it would be a pretty big deal! Captain Marvel is said to be the most powerful character in the MCU, so having her on the side against Thanos is a major get. Plus, it would be nice to think that the smallest Avengers officially bring Captain Marvel into the fold.
Of course, none of this could end up being the case and Ant-man and the Wasp could connect to these two Avengers movies in an entirely different way. The Ant-Man franchise is somewhat known for its low stakes amid the world-ending dangers constantly showcased by its peers, so it's exciting to think how this movie could connect to Marvel's grand Avengers double outing all the same. You can catch Avengers: Infinity War when it hits theaters on April 27, and Ant-Man and the Wasp will hit theaters on July 6. Here's what we know about the big Wasp debut.