The latest issue of the Official PlayStation Magazine in the UK, as reported by GameZine, contains a rumor that even though Activision has announced Call of Duty: Modern Warfare 2 to make a traditional release at the end of the year, its developers, Infinity Ward, are working on a new project as well.
The rumored project is said to be a game focused on assassination. Last year, a rumor surfaced saying that Infinity Ward was developing a sci-fi shooter. If we combine these rumors we get a sci-fi assassination game.
Official word can only confirm.