According to Whitten in an interview with IGN, "Like online, the console will still function if Kinect isn't plugged in, although you won't be able to use any feature or experience that explicitly uses the sensor."
Players will be able to turn off Kinect via system settings, and it will not collect any info. Users will be prompted if Kinect is needed, however.
"You can turn the sensor back on at any time through settings, and if you enter into a required Kinect experience (like Kinect Sports Rivals for instance), you'll get a message asking if you want to turn the sensor back on in order to continue," Whitten explained.
Whitten also confirmed that there won't be any cross-platform voice chat between Xbox 360 Live and Xbox One Live, though friends can still send text messages to each other. Xbox One and Xbox 360 users will also be able to see what the others are playing as well.