The event was suppose to hype Portal 2 related stuff, before being semi-cancelled on 2 June (it was postponed to 2011). This first announcement, however, suggested an E3 ‘surprise’ was being planned in its place, leading to amusing amounts of speculation over what this could be.
On 9 June, Valve grew tired of hearing Half-Life 3 rumors and let us know that the surprise would be Portal 2 information while also confirming that the title’s release schedule had slipped to 2011.
And now? Valve’s Doug Lombardi has circulated an email amongst the press stating "Just a quick note to clarify the Monday Press Event at the Regal Theater is completely cancelled. Please do not head over there expecting to see us."
The developer will still be present on the E3 show floor at the Los Angeles Convention Center, but whether Portal 2 will now be making an appearance in any form is unknown. Given the way this is going, we may just need to wait a couple more days for the whole thing to be back on again.