KH-Vids | Your ultimate source for Kingdom Hearts media

In an interview with IGN, Kingdom Hearts series director, Tetsuya Nomura, discusses the reasons for KH3's small delay, as well as why we haven't seen anything from the confirmed Big Hero 6 world yet. In regards to the delay, Nomura states:
As for why we still haven't seen footage of the Big Hero 6 world, the answer is pretty simple:
Source: IGN

GameStop has revealed that those who pre-order the deluxe Edition of 'Kingdom Hearts III' will receive an amazing looking fabric poster, which you can check out below:
However, supplies are limited, so you better pre-order quick if you would like to get your hands on this poster!

Source: GameStop

In an interview with Game Informer, the director of the Kingdom Hearts series, Tetsuya Nomura, confirmed that there are still more Disney worlds left to be revealed. Game Informer states:
As to the decision to revisit Jack Sparrow and the rest of the POTC gang:
And on the subject of DLC:
Source: Game Informer Link 1 & Game Informer Link 2

As the tweet above indicates, 'Kingdom Hearts III' will be one of the games focused on in the 'PlayStation Live From E3' program, with the focus on the game scheduled for 2:15 p.m. PDT on Tuesday, June 12th, which you'll be able to watch from live.playstation.com.

EDIT:

Here's the KH3 portion of 'PlayStation Live From E3':

'Kingdom Hearts III' is now available to pre-order from the PSN store (as seen above). Pre-order bonuses include a theme as well as a Star Seeker variant Keyblade.