As noted by Patently Apple, the June 2013 application shows off a few possibilities for the new technology, including a traditional combination lock-style system that has the user rotating his or her finger on the Touch ID sensor to input a security code.
Another potential implementation would require the user to swipe through a collection of circles by subtly shifting his or her finger in a specific pattern to unlock the phone. Both rely on the same technology created by AuthenTec that uses simultaneous security of a user's unique fingerprint and secure combinations to gain access to a device. AuthenTec has of course played an important role since its acquisition by Apple back in 2012, with the company's "Smart Sensor" technology serving as the basis for Touch ID.
While Touch ID was implemented for security reasons, the addition of a simple-to-enter secondary security code would increase security even further as a form of two-factor authentication combining physical authentication (fingerprint) with knowledge-based authentication (lock combination or swipe pattern). Implementation of such a system would address concerns over court rulings indicating that users could be compelled by police to unlock fingerprint-protected devices, unlike with passcode-protected devices.
The evolution of Touch ID from solely a fingerprint sensor in the iPhone 5s to the expanded "Reachability" features of the iPhone 6 and 6 Plus provides a hint at the possibilities of Touch ID in the future. And while inventions disclosed in Apple patent applications frequently do not ever appear in products, they can still offer some insight into Apple's areas of interest.