first off, I would like to say that this is my opinion but I have had it for a while now and would like to hear other people's opinion.
Now i would like to say this while i am at it, the Kinetic and MOVE are not the same, shouldn't be compared and in entire different categories. the move is a different controller like the analog for the PS1 in where that had its own analog only games and hybrids like the Move. The kinect is like the SegaCD and is a type of an Expansion onto the console again with its own games but no hybrids.
Now i would like to say that the closest thing to compare to the Kinect is the EyeToy and that is exactly what is going to happen to the Kinect, it will follow the exact same path as the eye toy in my opinion.
the kinect will sell big at first, so in this Q4 of 2010 and Q1 of 2011 will be the biggest period for Kinect sales, as it will be a Must have for 360 owners. It wont sell big on people buying the console just for the Kinect since its far to expensive, especially since its main market is the already Wii owners who can buy 2 wii's for one kinect/360 bundle. And since the 360 market is small due to splitting with 360 and PS3 in half and with the audience of 360 causal gamers who play violence games like halo, cod, gow they are not the type to turn around and buy kinect animal game. but people will buy on simply they want to have the 'New Thing" like 3D tv and the sega CD, but since the market is limited by 360 sales here is my sales numbers predicition.
Q4 2010-Q1 2011 -> 2-5 million sales
Q2 2011 -> on wards -> 5-15 million sales
Life time sales: 15-20 million units which will be 1/5 of 360 owners depending on the 360 sells 75 million units by 2015.
While that isn't bad, but software sales will be very limited, this type of hardware will see that its owners buy 1-3 games each, just like the eye toy with most people buying the one game that came with it and thats it nothing else. Kinect will be the same, as i cant see people buy titles for the kinect in large numbers and since none are hybrid publishes wont make top quality games for a limited market and if we are to see poor software results from kinect titles post release, then there will be a cut in kinect titles since it will be too expensive.
Kinect will last a year then fade away, Wii stayed alive due to a strong first party support from 20 years of games from Nintendo and an already existing fan base and also it was cheap. Kinect has an small fan base with its already existing fanbase not connected to the type of Kinect games. Move has its hybrid titles to keep the controller selling steadly. But kinect will rise then decline. I cant see people standing up and full body movement all the time for gaming, Wii users sit down majority of the time.
Of Course That's Just My Opinion, I Could Be Wrong