When will XB1 fall behind XB360 in LT sales?

[Dark_Lord_2008]

First 4 years sales of XBO can be close to or slightly ahead of X360.
X360 surprisingly sold well in its 5th and 6th years in 2010 and 2011.
This generation will be shorter and after 2017 its sales should fall behind the X360 ltd sales.
No way will XBO sell well in its 5th and 6th years. X360 is closing in on its 9th anniversary, XBO is closing in on its 1st anniversary. 8 years between the launches of X360 and XBO.