Microsoft has allowed Xbox One developers to tap into additional GPU resources in light of Kinect becoming an optional purchase for consumers, but this is not to be taken as a sign that Kinect functionality is entirely disabled should developers wish to bite into more Xbox One horsepower.
Ken Lobb, creative director at Microsoft Studios, explains to Eurogamer that "unlocking" an additional 10 per cent of the Xbox One's GPU bandwidth was intended to make the platform more flexible for game developers to work with. If they have no plans for Kinect support in their title(s), they have the option allow their games to leverage more GPU resources at their own discretion.
Kinect functionality will remain as integrated with the Xbox One as ever, but select features like game/system gestures and visual recognition can now be temporarily disabled if a game that chooses to tap into more GPU bandwidth happens to load up. Once the game is minimized to the dashboard, Kinect kicks back in thanks to new optimizations made to the Xbox One background operating system. Interestingly, Lobb stresses that at no point will voice commands be disabled, even during "Kinect-free" games.
As you expected, your ability to actually leverage Kinect simply depends on whether or not you actually have the peripheral, which will be available separately later this year. Unlocking the Xbox One GPU for use in Kinect-free games stills lead to "tangible" performance benefits no matter the hardware setup. A major example is the Xbox One version of Destiny, which managed to hit 1080p on the platform like the PS4 as a result of developer Bungie being able to tap into additional GPU resources. Lobb expects more titles to leverage the newfound GPU reserves by this holiday season.