Unfortunately, apart of the release date announcement is the news that the game has been delayed to 2019.
Square Enix has announced that Kingdom Hearts 3 will launch on January 29, 2019. We still might perhaps get some more gameplay at the conference though, so it might be time to get your hopes up. Confirmed worlds include Big Hero 6, Toy Story, Tangled, Monsters, Inc., and the returning Olympus Coliseum world.
A follow-up tweet noted that trailers and more information will be coming at E3. The gap between Kingdom Hearts 3 and Kingdom Hearts 2 will be just over 13 years.
The concert audience also got to see a new trailer for Kingdom Hearts III, which the rest of us should hopefully get to check out soon.