[stillmotion]

Word on the street was that they were planning on including both TouchID and FaceID in the X, but scrapped it earlier this year due to low yields during mass production[0].

[0] https://www.macrumors.com/2017/04/12/apple-struggling-with-t...

[MBCook]

Which is contradicted by this interview as well as discussions John Gruber has had with some of his sources.