AppleInsider found evidence of a new version of the existing Broadcom chip that supplies WiFi and Bluetooth on existing models jumps from BCM4325 to BCM4329. The component upgrade adds new support for 802.11n features, including the ability to find and join 5GHz networks.
9to5Mac notes that they neglected to mention that it also adds the ability to receive and send (the previous model could only receive) information through FM radio signals which theoretically could be used to broadcast sound into car stereos..without external adapters. It could also be used to pick up FM radio music, news and sports broadcasts on their iPhones and even, in August, on iPods. Currently the FM reciever is only used to pick up communications from the Nike+ peripheral.