And the first viral wave comes first with an icon placed within Call Of Duty: Black Ops 2 online gameplay maps embedded in the posters (as seen by @Drift0r), which provides a QR code to add Call Of Duty as a friend on snapchat.
So, having the viral campaign appear in Black Ops 2, one can only expect the next Call Of Duty game will be a Black Ops 3, which we seemed to have guessed right.