Apple is researching how to embed sensors into display panels, potentially enabling both Touch ID, and Face ID without a notch.
Future Face ID may not require a notch

Many of Apple’s recently revealed patents and patent applications, have been concerned with making more use of necessary components. That’s included a battery that doubles as a haptic feedback engine, and embedding Wi-Fi antennas in screens. Now Apple appears to be looking at just how much else can be included within an Apple Watch, or iPhone display.