A couple new hooks in the 4.0 APIs seem to indicate a device with a built-in flash. Yes, as in a camera flash:

AVCaptureFlashMode (auto/off/on modes)
AVCaptureDevice.hasFlash

Well, that could mean either a flash on the new iPhone (likely) or an external flash available as an accessory (less likely, but still possible). Or native pairing with certain cameras? That’d be insane. It’s all speculation at this point.