Insiders are speculating that the 3D ToF sensor will be added to the back of the phone, to enhance the AR functionality on iPhone 12 models, continuing the work started with ARKit 2 on iOS 12 (iOS 13 is bringing ARKit 3).
Plus, it will improve depth-based effects like bokeh and lighting effects in the camera app.
This sensor will be able to measure distances up to 4.5m away (15ft), longer than what current sensors on Android phones can manage. Apple was specifically looking for VCSEL components, which are what provide the pulses of light used by ToF sensors.
Note that the current 3D sensor on iPhones the TrueDepth system is based on structured light rather than time of flight (ToF). Time of flight modules offer greater accuracy and longer range, plus they handle sunlight better.