Modern Warfare 2 set records as the biggest media launch in history. You remember that this was the same year that Avatar was in theaters right? You had to know Activision was going to be following it up with a sequel.
You also had to know that E3 2011 would be the place for Modern Warfare 3 to make its debut. Activision has made a tradition out of showing off their upcoming Call of Duty games during Microsoft's E3 press conference. Having Call of Duty lead on Xbox 360 means it's a big promotion spectacle for the two industry giants.
You also had to know that a game as big as Modern Warfare 3 wasn't going to sneak into E3. Official PlayStation Magazine dropped the teaser in this month's issue that they'd have a huge reveal for the world in June. You can see the splash page above. Apparently Craig Fairbrass has been dropping hints as well:
I did Call of Duty: Modern Warfare as Gaz and then I did Ghost in Modern Warfare 2, which has become one of the more iconic figures in the history of computer games, which is great. And I've just been out in LA doing something that's going to be announced in May. I've just been out there doing some bits and pieces, and one is to do with... I can't say too much.
You're welcomed to fanboy-out about Call of Duty in the comments, and maybe you'd like to Internet-Shout at me for saying this but Ghost does not deserve "iconic figure" status in video games.