A silent update to the backend has introduced Genius recommendations for movies and TV shows to the Apple TV. No user action is required to access the new feature, as it's not part of a device firmware update. Instead, Apple has updated its own servers to send this information to the Apple TV from its iTunes Store equivalent.
Based on AppleInsider's screenshots of the updated Apple TV UI, this feature appears essentially identical to the Genius recommendation features already present in iTunes on the Mac and iOS devices. With access to your library and purchase history, the Apple TV can now recommend TV or movie content based on what you've watched before.