The Cake Is Truly A Lie, But Portal 2 Is Not Portal 2
Portal 2
Portal 2
Portal 2

Or you could pop on over to the GameStop site and scope out these details listed under the PC description for the pre-order. A description that states there is going to be a full new cast of characters, a load of new puzzles, much larger puzzles as well, and multiplayer/co-op modes in the game. Yea, Portal went co-op/multiplayer. That just happened.

UPDATE: The listing of co-op/multiplayer has been stripped from the site, but below is the original posting. Just in case they pulled it because Valve asked them too and not because their content manager messed up.

Coming this holiday. Portal 2 is the sequel to 2007's Game of the Year and draws from the award-winning formula of innovative game play, story, and music that earned the original over 70 industry accolades. Features single and multiplayer co-op modes. The single-player portion of Portal 2 introduces a cast of dynamic new characters, a host of fresh puzzle elements, and a much larger set of devious test chambers. Players will explore never-before-seen areas of the Aperture Science Labs and be reunited with GLaDOS, the occasionally murderous computer companion who guided them through the original game. The game's two-player cooperative mode features its own entirely separate campaign with a unique story, test chambers, and two new player characters. This new mode forces players to reconsider everything they thought they knew about portals. Success will require them to not just act cooperatively, but to think cooperatively.

Source: Game Informer

And if that isn't enough Portal news for you, there has been a new patch for the first Portal. Not to mention the alternate ending for the game. Looks like the cake really is a lie here. But rest assured that the announcement of Portal 2 is not.