Spoilers for Avengers: Infinity War and Ant-Man and The Wasp follow. Major spoilers!
To conclude Avengers: Infinity War, Thanos snapped his fingers wearing the Infinity Gauntlet and accomplished his mission of erasing half the universe. Two months after Infinity War hit theaters, Ant-Man and The Wasp released, revealing all sorts of details regarding the quantum realm which many suspect will play a role in the remaining Avengers' efforts to undo Thanos' deeds.
However, the seeds for this may have been planted in Thor: The Dark World. Reddit user leafinferno pointed out that Jane Foster talked with Asgardian doctor Eir and was informed of a "quantum field generator" which "tranfers molecular energy from one place to another." In short, Eir tells Jane it is referred to as a "Soul Forge."
This would seem to indicate Asgardians could be sending souls to the quantum realm, which is fueled further by its alignment with a theory spawning from the Ant-Man and The Wasp post-credits scene. When the ending scenes from Avengers: Infinity War are chronologically lined up with Scott Lang heading into the quantum realm, it appears the souls disappearing from existence might be reappearing as orange gems of energy buzzing through the microscopic part of the world. The Soul Stone, after all, is orange.
This could mean a number of things which are yet to be revealed but one is that Asgardians might have an idea regarding how to send the living into this Soul Forge where they may encounter Scott Lang and/or a time vortex. In fact, the possibilities are endless and each only raises more questions.
Of course, it's possible the colors flying around Scott Lang in the quantum realm are the healing particles respawning after he collected most of those surrounding him at the time. It's more fun, though, to speculate as the wait for the Avengers 4 trailer and actual release continues.
Avengers: Infinity War and Ant-Man and the Wasp are now available as a digital download as well as on Blu-ray and DVD. Upcoming Marvel Cinematic Universe movies include Captain Marvel on March 8, 2019, Avengers 4 on May 3, 2019, and Spider-Man: Far From Home on July 5, 2019.