Every iPad has had right angles up to now. This also applied to iOS handsets to the iPhone X. And now it seems that Apple is wearing this design element on all its devices. For example, each of the 2018 iPhone models has rounded corners.
And the Apple iOS 12 simulator has an iPad mask so the corners of the screen are also rounded 9to5Mac. It is made for models called J3xx, apparently the internal designation of devices iPad Pro 2018.
Other changes to iPad Pro 2018
Replacing Touch ID with Face ID will cause many changes in the next professional iPad. This removes the need for the start button, allowing Apple to reduce the size of devices.
A small image of the iPad Pro 2018 buried in the latest iOS 12 beta has apparently confirmed the redesign. Surprisingly, there is no screen cutout such as the famous screen of the iPhone X.
A permanent mystery is what looks like a new port just above the Lightning port on a leak pattern. What is it for now?
The new iPad Pro offers are expected this fall, probably after the start of the iPhone 2018 models in September. They will certainly appear before the beginning of the year's end holiday.