Take this post with a grain of salt, but CNET UK believes the Xbox One will be launched November 29th based on information obtained from retailer Toys R’ US. Sony is releasing their console in mid-December, so an earlier release by Microsoft would be a blow to Sony and would help the Xbox One pick up some more momentum. Amazon, which give estimated dates for pre-orders, has also pegged the Xbox One launching in November 2013. The PS4 is currently priced a $100 cheaper than the Xbox One, but it does not include a bundled version of their equivalent Kinect technology.
Source: CNET UK