Super cool! Check out a fan edit featuring the Ant-Man and the Wasp post-credit scene coupled with footage from the end of The Avengers: Infinity War!
Obvious spoilers follow.
While it wasn't shown in Ant-Man and the Wasp, the end of the movie (or soon after) took place right around the same time the huge battle in The Avengers: Infinity War happened in Wakanada between Thanos and his forces and the Avengers.
The way they did the Ant-Man and the Wasp post-credit scene was actually really cool as it kept things as a surprise--we didn't know when the events in Infinity War were happening; so what went down was a big surprise!
The Ant-Man and the Wasp post-credit scene is eerily similar to Infinity War's own post-credit scene:
Hank Pym, Janet Van Dyne and their daughter Hope are helping Ant-Man while he goes back into the Quantum Realm to aquire energy to save and sustain Ghost. There are some jokes dropped in the scene, which leads to you possibly thinking everything is all hunky-dory. Hope then starts the countdown for Ant-Man's re-entry - "5, 4, 3" - and then it stops, leading to Ant-Man thinking they are joking around. However, what happens next is a result of the Great Titan's "Snappening" as it's revealed Hank, Janet and Hope have turned to dust! This leaves Ant-Man seemingly lost in the Quantum Realm!
Small tidbit: The Russo brothers have stated the reason Ant-Man surviced is pure chance, and not because he was in the Quantum Realm at the time of Thanos' snap.Â
Regarding the Infinity War post-credit scene, it featured both Nick Fury and Maria Hill turning to dust as well!Â
Check out the fan edit, which makes a pretty good attempt at correlating all the footage: