I put the link in post #9, but apparently Federighi said that there may be situations where different biometric techniques or a combination of them could make sense. Can’t remember if it’s from the same link but he also says Face ID won’t work in all situations, so that’s likely the reasoning behind the first statement—no biometric technique is perfect for all situations.Apple would never have released FaceID in the first place if they didn’t think it was more than good enough to replace TouchID in its entirety - there was never any chance they’d put both in the same device.
Point being, while it’s clear Apple has bet big on Face ID, it doesn’t sound like they consider it to be the end all. And it sounds like they left open the possibility of multiple biometric techniques in the same device, which could mean both Face ID and Touch ID. That said, I don’t think it’s likely they would put them both in an iPhone now if they haven’t yet, unless it’s because they wanted to integrate Touch ID under screen but haven’t been able to yet.