As you know the climax of the Avengers Infinity war is quite confusing..As many of the heroes disintegrates and mixes with air bcoz the Thanos got all the infinity stones.
Dont Worry
I am here to explain the climax.
https://goo.gl/images/RR3phB
The soul stone got special powers as it can take half of the souls in the universe and keeps them in separate dimension. So there are many chances that they can make a comeback in part 2 of the film.