Valve have just announced that they've replaced their planned Portal 2 event during E3 with a "surprise". What the surprise is? We don't know. It's a surprise. As Valve, and Aperture Science, tell us:
"However, per international treaties regarding the definition of the word 'surprise', of which both Aperture Science and Valve are signatories, the time, date and content of the actual surprise will only become available as you experience the surprise".
Will there be cake? Perhaps.