In such a scenario where there is no fingerprint sensor, Apple will have to rely entirely on the front 3D camera to allow for biometric login procedures.
With iPhone 8 launch drawing closer by the day, it is only natural for rumors about it to pick up pace. Take for instance the latest on this, which claims the upcoming anniversary iPhone model to have no front mounted Touch ID sensor at all.
The above stems from the thought process that Apple could have run into some issue trying to place the Touch ID sensor behind the front display. If that is indeed the scenario, the options for Apple to explore will be to either have the fingerprint sensor placed behind the device or to eliminate it altogether.
Further, in the latter scenario with the iPhone 8 doing away with the fingerprint sensor entirely, this again could be an indication of Apple having reached a fairly advanced stage with its front-mounted the 3D sensor to be employed as the primary tool for biometric authentication. That would require it to perform flawlessly even in adverse light conditions or when pointed from odd angles, technological challenges that Apple seems to have surmounted successfully.
Yet another but less desirable option for Apple to go for will be to postpone the launch of the iPhone 8 till it has perfected the technology to have the Touch ID sensor integrated beneath the front display. Apple is reported to take the final call on this shortly.
The usual place for the sensor since its inception has been underneath the home button. However, with the iPhone 8 all set to incorporate an OLED panel that would make up the entire front end, Apple either has to find a way to place the Touch ID sensor underneath the touchscreen or have it shifted to the rear of the handset as most high-end Android devices have resorted to.
Another rumor doing the rounds is that Apple might consider having in place a stainless steel rim similar to that of the Apple Watch. Such a rim would serve as the chassis of sorts for the front and rear panels to be attached to ensure the overall rigidity of the device remains intact.