This is giving me a bit of a brain wave. There are three prejudices present as part of Zootopia's specism. Pred vs Prey, Large vs Small, and specific species stereotypes right? Judy perpetuates all 3 at some point in the movie. The one out of the three that isn't obvious is large vs small. Her meeting Mr. Big for the first time and specifically her body language in the scene. In this case she's bigger and slightly dismissive without realizing it because she's used to being the little guy.
As for a Zootopia 2 story...Well it depends on the direction they want to go. They could double down on the buddy cop angle with a caper. A high profile thief job with a specist scapegoat would carry forward the themes from the first movie. (I mean that the real thieves plant evidence pointing at idk Raccoons.)
Where it gets hard to speculate is if they try to go for a different theme / message. I'd kind of like to see that more. Let some specism exist in the background and have the characters address it when it comes up but don't make it the cornerstone piece of the plot again.