At 7 million copies of CoD 4 sold, this is hardly surprising.
I imagine if they did an online survey of most of the people who bought their games, a small percentage could have said yes, and that would have been enough to move this forward and make it happen. People love CoD enough to pay for this, this is fact.
From a gamer standpoint, this is horrendous, and they are getting greedy.
From a business standpoint, genius. People ARE going to want these minor things, especially when they see people running around maps with 'cool looking gear' (which you could easily do yourself in CoD 4 PC). If this game actually sells more than Modern Warfare 2, they could be buying a small country in the future.