iPad Mini 4 is on its way, but we have got some news for you. iPad Mini 4 will have 6.13mm thickness only that is 1.37mm thinner than iPad Mini 3. Apple is working hard to make the devices slim to give them a great look. Apart from thickness, its width would be 134.75mm and the length 203.16mm. So here is the exact dimension what you are going to get with iPad Mini 4 : 203.16 x 134.75 x 6.13 mm.
iPad Mini 4 3D CAD Video
The leak is coming from @OnLeaks, and they provide the most accurate leak about Apple devices. They also provided the leaked housing images of iPad Mini 4 that you can see below.
iPad Mini devices are always one year behind than iPhones in terms of chipset, so you can expect Apple A8 chip with them. It will also be launched with iOS 9 OS like iPhone 6S and 6S Plus.