By next year the iPhone 8 should be entirely discontinued from the lineup, completing the transition for all iPhones having Face ID. Add to that, dropping the price of the iPhone 11 to $699, and also the iPhone XR to $599, making it the cheapest entry Face ID device today. Assuming next year that the iPhone XR drops another $100, down to $499, they will have hit the iPad Air price point so I don't see why they wouldn't be able to start trickling the technology down to the iPad line. I understand not adopting Face ID to the iPad or iPad mini (at least for a while), but the Air has to be next in line for Face ID treatment, either in 2020 or 2021!