I'm thinking Xbox One will go for $399.99 in December and still come with Kinect, which means Microsoft will be giving the Kinect away.
The problem for Microsoft is that they are just barely breaking even on each XBox One unit sold right now, and when you look beyond the cost of each unit sold and consider the entire XBox One operation costs then Microsoft is losing big money on the XBox One right now. If they were to cut the cost $100 they would be taking a really steep loss and it is still far from certain that they could move ahead of Sony in sales even with that price cut. Cutting the price that much would be a huge risk and if it did not pay off with huge increases in software sales then Microsoft's gaming division would sink deep into the red.
Microsoft is between a rock and a hard place, they can not beat Sony in price unless they drop Kinect and if they drop Kinect they will lose hundreds of millions of dollars. I suspect Kinect will eventually get dropped, but it won't happen easily. Microsoft really does not want to abandon it, but if abandoning it is the only way to compete with Sony they may have no choice.