A handful of photos of cases for Apple's upcoming iPad Mini leaked this morning on GizChina. The cases back up previous rumors that the device will have a ~7-inch screen, smaller nine-pin dock connector, and a thinner bezel than the current 10-inch iPad.
Apple will supposedly announce its smaller iPad this fall. Apple evangelists John Gruber and Jim Dalrymple floated some informed speculation last night that the company will unveil the iPad Mini a few weeks after the September 12 iPhone 5 event, likely in October. (Those guys are very close to the company, so we're inclined to believe them.)
Third-party case manufacturers typically start making accessories for Apple devices months in advance of launch. They rely on supply chain leaks to get specs and measurements, but as we learned last year with the iPhone 4S launch, those leaks aren't always correct.