Xbox Kinect Will Work as Headset
If you don't want to spend extra money on a headset after buying the Xbox One, you'll be happy to know that the Kinect will also back up as an alternative to the microphone/headset.
There's no official word on the quality of the Kinect microphone, and you'll have to listen to players through your TV unless you have a pair of compatible headphones when using the Kinect for voice chat.
The Kinect does include a 'wide array' of microphones though, so it'd be surprising if the call quality received from the Kinect was poor.
The official Xbox One is always up for grabs for those that don't like the openness of the Kinect microphone and TV speaker combo, and there are also many alternatives for better audio quality including headset models from Turtle Beach specifically designed for the Xbox One.