Counterpoint: You're naive if you think there are dozens of unannounced AAA Kinect games waiting to be announced based on zero precedence on the 360, with zero devs making public statements announcing investment in the device as an exclusive input, and zero evidence (leaked or announced) that MS' first party is using it for anything more than party and casual games.
Do you know why Kinect Sports and Fantasia were announced first? Because they are the highest profile Kinect games in development for the launch window. Even though neither game will be ready in November, MS needed something to explain why the thing was in the box other than the UI...
...which brings me to my second point. If MS was that serious, they would make Kinect mandatory for UI navigation. But since MS is a business, businesses have to hedge their bets, which is why they designed it from the outset to be navigable via the default gamepad. Kinect is to One as touch is to Windows 8 - the UI was obviously devised with it in mind, but you'd have to be braindead to release a PC OS that doesn't accept mouse/KB inputs, just like you'd have to be braindead to release a console UI that doesn't accept controller inputs.
It is an accessory, because 95% of the game library does not require it to operate properly. That has always been the definition of an accessory. Contrast this to the WiiMote, where 95% of the game library flat out did not work without it. Go the XboxOne home page:
http://www.xbox.com/en-US/xbox-one/xbox-one-games?xr=shellnav
4 out of 44 announced games require Kinect.
Peripheral.
No backwards compatibility, and controller familiarity/platform history didn't do jack shit for people who jumped ship for DMC4, GTA4, RE5, and Madden. $100 is a $100. Casuals don't care about the name on the box, the PS3 at $599 proved that.
Situation C is happening RIGHT NOW, even with the DRM/used game/indie reversals.