New code found in iOS 7.1 and iOS 7.1.1, suggests that Apple is working on building support for Siri on the Apple TV. References to a new Apple TV were previously found in iOS 7 builds and the new strings suggest that voice input and feedback will be included on the next gen devices.
The file is a supporting property-list resource for Assistant (Apple’s internal name for Siri), containing information about the feature. The UIDeviceFamily array declares what platforms are compatible with the feature.
As shown by Apple’s documentation, ‘1’ and ‘2’ represent the iPhone/iPod touch and iPad families. The ‘3’ represents the Apple TV family.