During an interview with IGN, Marc Whitten from the Xbox One team has noted that the Kinect will not be needed in order for Xbox One to be used in full.
He noted that the console will still normally function even when Kinect is not plugged in but that users will not be able to use any features or get the experience that explicitly depends on the sensor. He further explained that the Kinect can be turned off in settings and will not collect any information in that mode but any functionality that relies on voice, video or gesture simply will not work.
Future console gamers have been putting a lot of pressure on Microsoft's always-on decision for Kinect and it appears that Microsoft finally gave up under pressure and decided to implement "off" switch in the settings menu.
Source:
IGN.com.