In all actuality, this is most likely a nice little tease for what Activision is going to show off at GDC. The counter on the site just happens to end when GDC begins and what better way for Activision to begin the show than with one of the few franchises it is leaving up and running. It makes perfect sense to me and it really should to everyone else out there that contributed to the 20 million (plus) copies sold franchise. If not, then you really need to figure out why you bought the game and why you thought that there wouldn't be a third.
That said, wouldn't it be amazing if this was some internet hoax? Could you imagine the outcry and whining that would occur on websites the world over? I mean it could actually shut down businesses as their entire let down workers simultaneously logged on to bitch about it being a ruse. Hells I could see every news and blog site getting bombarded with comments and email containing "Why would you tweak my nipples with a possible announcement that turned into a hoax?" Oh gods I hope it is a hoax now. I love reading hate mail.
How about you there reading this because you saw Modern Warfare 3 in the headline? Oh wait; you would be the hate mail/commenter wouldn't you? Let's see how this plays out when GDC starts and the counter hits zero.