Looking at the comparison photo below you can see that there are differences at the top of the frame that houses the camera, sensors, and speaker.
Apple is widely expected to improve the camera of the iPhone with its next generation device. Rumors peg the camera at 12MP with improved low light and HDR capabilities. In April, the front facing camera for the iPhone 5S was allegedly leaked.
Although Apple is holding a WWDC keynote on Monday, the company is not expected to unveil the iPhone 5S until fall.