The Kinect may have some success on the PC because of the many billions of PC users, so there probably be a few million to hundreds of thousands of users who are interested in Kinect and motion gaming.
Almost everyone in North America, Europe, Asia, Australia, and parts of Africa have access to a Windows, Mac, or Linux PC or laptop, and there are many different types of gamers on PC who like different types of games like Flight Simulators, Sims, MMORPG, Real Time Strategy, and Puzzle games which are not as popular on consoles compared to RPG, Action, adventure, and shooters which are popular on consoles, and PC as well.
I think the Kinect could be popular with Smartphone, and Tablet users if MS makes Kinect work on mobile devices because of the amount of people who owns a smartphone and tablet. The Kinect could be a good controller for certain types of mobile games like Clash of Clans, Tower Defense, and games where you need to move things around a lot.