The second pre-show includes guests watching a screen which includes Rocket and Groot and the Milano.
The queue will then move into a pair of pre-shows, the first is being called “singularity.”
Concept art shows the Milano to also include other Guardians characters, so its possible that the entire Guardians of the Galaxy cast will make appearances, in the same way they do in Guardians of the Galaxy: Mission – Breakout at Disney’s California Adventure.
As Walt Disney World News Today points out, that’s the same word The Collector used to describe the Infinity Stones in the first Guardians film, so it’s possible this show will reference one or more of the stones, though there are no details that confirm that.