Preview at WWDC likely in June, followed by September launch.
Details Emerge Regarding 'Face ID' Setup Process on iPhone X
Rambo tweeted the settings and preference screen for Face ID, where you can choose to use Face ID for iPhone Unlock, iTunes and App Store, and Safari Autofill. Apple Pay is missing from the page, but Rambo noted that it's most likely because he's using a Brazilian Apple ID and Apple Pay isn't available in Brazil.
Face ID enrollment process (with layout issues on first page) pic.twitter.com/KczOHEy9ir— Guilherme Rambo (@_inside) September 9, 2017
In another video, Rambo recorded a separate piece of UI related to Face ID that he described as "authenticating with Face ID." This is expected to be another step in Face ID's setup process, but Rambo pointed out that he's "not sure" there will be a camera preview in the final version of the software. He did say that the smiley face glyph and rotating sphere animation will be parts of Face ID to some extent.
Authenticating with FaceID looks like this (timing not correct because it's just the UI, not actual auth) pic.twitter.com/kvNUARDQBJ— Guilherme Rambo (@_inside) September 9, 2017