Major Nelson just confirmed the pricing of Kinect at $149, along with a new 4GB Xbox 360 which will be priced at $199. This new Xbox 360 will include built in Wi-Fi N, 4GB of internal flash memory and a black matte finish(not all glossy like the 250GB Xbox 360). The new 4GB Xbox 360 will ship August 3rd, 2010.
Last but not least, there will be an ultimate holiday bundle with the Kinect and the 4GB Xbox 360 for $299.
The complete details are on Major Nelson's website.