A recent APK teardown conducted by both AndroidPolice and 9to5google reveals that Google might consider scanning your face in order to improve the functionality of Assistant. Similarly to how Voice Match works, Face Match (tentative name) would scan your face in order to enable tailored commands on devices that are equipped with cameras.
This feature will be different from the Face ID-like functionality that Android 10 Q could natively bring once it will be officially revealed. Details are scarce, and usually those coming from early APK teardowns may or may not make it to the final build. However, the report claims that one will be able to train the system and add multiple profiles that are available across multiple devices.
Considering the scarce details, it’s not certain when, if ever, this option will be available. However, if it does, it could enable users to issue commands without a voice profile, which, by itself, could also be regarded as an accessibility feature. We’ll keep an eye out for further details.