They could just be overshipping now so they can use their factories to make a lot of X720s (rather than X360s) in the holiday quarter. That was part of the reason the original Xbox was phased out earlier than necessary. Instead of making 3-4m X360s in Q4, they can make 2-3m, and 1-2m X720s too.
Overshipping? not this again.
You cant overship, retailers can over-order. Retailers wont be over ordering a console at the end of its life. 6 months supply? come on man.
Its hugely undertracked. Pure and simple. The tracking in the "rest of the world" is just way off.