I normally use my iPhone for my flights but sometimes I use my daughter's iPad Mini 3, when I want to have more screen size / details for planning my shots or if I have somebody looking over my shoulder. It is still update-able to the latest iOS version and will be compatible for DJI Go4 for quite some time in the future.
So for me, it's a very good but still compact screen for flying, keeping in mind, that the iPad Mini 4 is still very expensive, compared to the larger, "normal" iPad.