With the release of the 4th Beta of iOS 7 this morning, root files in the  ‘Accessibility’ area of the system points to a ‘biometric’ kit. Lines of code in the kit display text such as “Photo of a person holding an iPhone with their left hand while touching the Home button with their thumb ” and “A fingerprint that changes colour during the setup process.”. This almost certainly confirms that a fingerprint sensor will be present in the next generation device. Judging from the text, the sensor may be on the home screen button, and act primarily as a security and/or accessibility feature.