The story oversimplifies the issue and doesn't quite get the Rancho Cucamonga Quakes' dinosaur mascot case right. I was a bit surprised to see it referenced. It isn't even part of California case law. The ruling is only authority in California district. And it doesn't seem to be as on point as the story makes it out to be. But in these electronic times, if you're an attorney arguing a case, West makes it easy to find rulings that might be persuasive.
Most such litigation against sports teams has to do with fans getting hit by baseballs, bats, in whole or part, and hockey pucks. I've looked, and the only such case where I've ever seen where a fan prevail was when the Quakes mascot had his tail in a man's face, distracting him and preventing him from being able to react to the foul ball that injured him. The mascot didn't injure the fan. The mascot had nothing to do with the foul ball that did.
Part of the point to the foul/thrown-ball cases, though is that teams don't have control over such things and fans carry an assumption of risk. Mascots throwing things into the stands should be different. In this Royals case, the injury was caused by the mascot. Without knowing more specifics than the brief coverage provides, it looks like this fan has a case.
This case seems to be something entirely different from the foul-ball stuff. And case law is needed in this specific area because it's only a matter of time before a T-shirt canon begins taking out fans.