Nowhereelse.fr and other sites have speculated that the part is related to camera functionality given its proximity to the front and rear cameras on the iPhone, but we chatted with iFixit's Miro Djuric and determined that it appears to be primarily related to wireless antenna functionality, although its exact role has not been confirmed.
The corresponding iPhone 5 part houses a low noise amplifier from Skyworks that is involved in cellular connectivity. The part shown in the new photos also contains an antenna connector, which appears to correspond to one located nearby on the main logic board in the iPhone 5. That iPhone 5 connector is believed (but not confirmed) to be for the device's Wi-Fi antenna.
While Apple has tweaked the layout of this part somewhat, it is very similar to the corresponding iPhone 5 part and does not immediately reveal any major changes for the device that will use it.
Minor parts for the next-generation iPhone have been leaking over the last several months, although identification of the devices associated with those parts has been made more difficult by rumors that Apple is looking to introduce both an iPhone 5S and a lower-cost iPhone later this year. In past years, Apple's strategy has been to release just one new model while keeping previous models available at lower price points.