E3 Portal 2 event replaced by "surprise"

Valve has announced, via a quirky email, that the Portal 2 E3 event has been replaced by "a surprise".

"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," the email reads.

Could this be the unveiling of Half-Life 2: Episode Three?

Valve will still be showing Portal 2 at E3 to press by appointment. E3 takes place from 15th to 17th June at the LA Convention Center.