I doubt any game will ever require it.
That's the nature of peripherals. How many games required the Classic Controller on the Wii? And how many games required the Motion Plus peripheral? That's always the way things go with peripherals. That's why if you want a feature to be supported it has to be INTEGRATED BY DEFAULT. If its not there by default, developers won't support it.
TJ says Nintendo will not integrate it until there is at least one game that requires it, but this is a catch 22, because no game will ever require it until it is integrated. So if it isn't integrated it will never happen.
There were Call of Duty games on DS and that didn't have 1 circle pad.
The key word here is "were". I think the last one was Black Ops which came out in 2010 which was two years ago. MW3 didn't come to the DS nor the 3DS, and there has been no announcement of Black Ops 2 either so that probably won't happen. What is your explanation for this?
And before you point out that the 3DS doesn't have the install base that the DS has, let me point out the Vita is getting it and its install base is even smaller than the 3DS. So that can't be the reason.