Granted not by much (around 4.2% from what I read) but it seems that this could be the start of it falling out of popularity. I wonder if Black Ops 2 can fix this or if we will see it go even further into decline.
http://www.gamasutra.com/view/news/168543/Call_of_Duty_sales_slow_down_as_casual_buyers_find_entertainment_elsewhere.php
http://www.gamasutra.com/view/news/168543/Call_of_Duty_sales_slow_down_as_casual_buyers_find_entertainment_elsewhere.php