There's little consensus on specifics, but a number of rumors suggest that Apple is planning wireless charging and new types of biometric authentication for the iPhone 8. In terms of biometrics, that could be iris or facial recognition, or possibly a modified fingerprint sensor. (Iris scanning was one key feature of Samsung's ill-fated Galaxy Note 7, pictured.) The physical home button -- where the fingerprint sensor is located right now -- may be on its way out with the iPhone 8, some reports say.
Stronger water resistance is also rumored for the iPhone 8 (IP68 instead of the current IP67), as is a 3-D-sensing camera (for augmented reality and biometric authentication). Meanwhile, other specs are also expected to get a boost in the iPhone 8, including the size of the battery and the processor.