AirPlay currently requires an existing Wi-Fi network in order to stream media or mirror content from an iPhone, iPod touch, iPad, or Mac to an Apple TV or speaker system. This makes it more cumbersome for non-technical users, and less convenient for temporary situations like guests or traveling. Something like Wi-Fi direct, which would allow device-to-device connections would be a simpler solution. According to Matt Warman of The Telegraph, exactly that kind of "Airplay Direct" feature is in the works for iOS 6 and the iPhone 5:
Sources familiar with the iPhone-maker’s plans said that Apple wants to improve the AirPlay wireless music streaming technology, which currently requires Airplay speakers and a WiFi network. The new version will require just speakers or a hifi and an iDevice; the iPhone, iPod or iPad would form its own network to allow a direct connection and music playback.
If Apple does indeed go ahead with an "AirPlay Direct" feature, it seems likely it could use Wi-Fi Direct as its foundation. A Wi-Fi Direct enabled Apple product line raises a lot of interesting prospects beyond AirPlay. AirDrop, or wireless file transfer, will not doubt leap to mind. But direct Wi-Fi sync and many other types of point-to-point data transfers could be possible.
NFC may be off the table for the next iPhone, but with Bluetooth 4.0 already on board, and the possibility of Wi-Fi Direct, both of which might well be more secure than NFC anyway, Apple might not be missing out on much, feature-wise.