Or they just got off a vacation, and couldn't excuse taking off the time after to attend a con, rather choosing to work... I would guess :P

Doub't it. Doubt they could even get the teaser trailer done by then.

Devs already said they would not

I believe its because they don't want to show how little they have done, but im sure its to surprise people with the great update and they just couldn't get a slot:P