Apple will probably add Face ID to a next version of the iPad. The iOS 12 beta includes support for AvatarKit for iPads. To make use of this, a so-called TrueDepth camera is needed.
A developer notes on Twitter the presence of AvatarKit support for iPads on. The interface has been adapted for larger screens, among other things. AvatarKit allows users to create so-called animojis, which are emojis that move. Now you can only do that with the iPhone X and it works with the front camera and sensor, which can measure depth. Apple also uses this technique for Face ID, unlocking the phone with facial recognition.
If Apple releases an iPad that offers the ability to create custom animated emojis just like the iPhone X, it is likely that the tablet will have similar hardware as the phone. By providing an iPad with the so-called TrueDepth camera, Apple can also add Face ID.
Last year there was already a rumor that Apple would equip a new iPad Pro model with thinner screen bezels and Face ID. The home button would also disappear from the housing.