Countdown appears on Aperture Science site. World initiates preload

A countdown has appeared on www.aperturescience.com , along with a message from the ever-enchanting GLaDOS.

She seems pretty happy with humankind's progress through the Valve Arg over the past few days, but what could the countdown actually be leading up to?

Office speculation is rife: the early release of Portal 2? The early release of a bit of Portal 2? A mini Portal 2 mini-game thing? Companion Cube plushies for everyone? Some Half-Life 2: Episode 3 info? More potatoes?

Initiate speculation and mild panic... NOW.