Square Enix will be hosting a special Final Fantasy XVI event just ahead of its release date. This 'pre-launch celebration' will take place in Los Angeles on the 11th June, and it'll be livestreamed. Outside of this basic information, we don't really know what the event will offer. The publisher says there are "more details to come". Stay tuned, we suppose!
Given the timing of the event, it could be that Final Fantasy XVI's playable demo drops during the stream. Said demo was confirmed quite some time ago, with producer Naoki Yoshida saying that it would launch close to the game's full release. Seems like a perfect opportunity to us.