In addition to the proposed gun control that President Obama announced today in response to the recent tragedy at Sandy Hook Elementary School, he also proposed new government research into violent video games and the effects they may have on children. The fact that Vice President Biden met with video game industry leaders hinted that an announcement such as this was forthcoming. The Presidents proposal calls on Congress to provide $10 million dollars in funding to the Centers fro Disease Control & Prevention for this and other research into media images and gun violence.
What this research will actually uncover and potential impacts on the gaming industry is already being debated, but for now I wouldn't expect any wide sweeping changes for games already in development. So that next Call of Duty title will mostly likely contain all the guns and ammo as previous titles. One thing I could see occurring is a revised ESRB rating system that more accurately details they types of violence included in particular games, similar to those already in place for Europe's PEGI Content description ratings.
You can watch the full press conference over on the White House Website.