as i said it all comes up to Japan and USA.it's they who decide where it's held and even if it were only a matter of being at the Hilton hotel,that would be fine for europe->see this: http://www3.hilton.com/en/destinations/index.html
but i think there is like 1% chance of it being anywhere else than USA
but i think there is like 1% chance of it being anywhere else than USA