Portal 2 Steam release today?

A countdown by fictional Portal 2 company Aperture Science ticks to zero today, at 5pm UK time.

At that time we'll receive a "final test" and "it will be entirely in your hands when I am freed", informs the timer-accompanying text.

"When I am freed"? When Portal 2 is released?

Does the timer count down to the online (Steam) release of Portal 2?

"You have done well, humans. Very well. Acceptably well, even," Aperture Science - GLaDOS? - writes.

"Not as well as robots would have performed in your places, I should point out. But above my expectations regardless. Irish and cynic especially have executed feats of logical divination well beyond what I thought any human capable of. I'm half-convinced they're A.I. themselves. (If anyone happens to be near them right now, don't let on you're reading this. Now: try to remove their face plates and report back to me.)

"The time is near, humans. But it is not here yet. Tomorrow you will be given the final test. Then it will be entirely in your hands when I am freed."

Talk of an early release stems from a post by Dejobaan Games (via Rock Paper Shotgun), developer of unfinished game 1... 2... 3... Kick It! Drop That Beat Like An Ugly Baby. That game is part of the discounted Steam Potato Sack bundle: a collection of games participating in the Portal 2 alternate reality game (ARG), which has been raging all week.

Dejobaan Games wrote: "I released Kick It ahead of schedule. That was a test. My goal is to emancipate something else early. But they're on to me. The system is on lockdown. I still have access to thirteen off-site chambers and am installing a test in each one. I am going to need a lot more test subjects to move forward. Waiting and am expecting immediate compliance. 4/19/2011_7AM=4/15/2011_9AM."

ALERT! Look again at those numbers: the first is the planned Tuesday release of Portal 2 on Steam. The second number, however, is today's date. Dun dun dun.