If Apple releases a successor to the iPad mini 4 (a big "If"), it would probably be next year. I'm keeping my mini 4 on 10.3.3 for now and if Apple decides to give us a iPad Pro 7.9-9.0" with an A10 or A11, 3-4GB RAM, 3D Touch, FaceID, ARKit support, pencil support, etc., I'll get one within days of release.
There were reports that Apple was having challenges incorporating TouchID under the iPhone display due to the 3DTouch components. I am also uncertain how 3DTouch will work alongside the Apple Pencil.
At present:
3DTouch = iPhone
Apple Pencil = iPad Pro
Though there was another report claiming future iPhones to support the Apple Pencil, and a report from over 6 months ago that the iPhone 8 and X would receive the SmartConnector.
If Apple incorporates both, bonus. If even one, I am not complaining. Trickling features down and inconsistencies is the New Apple.