The Kingdom Hearts name has been referred to many times in the existing games of the franchise, however, no specific details regarding it has been divulged by the developers as of yet.
The YouTube channel The Gamers Joint claimed that this place might be made of pure light and thus it will be just the opposite of the Realm of Darkness. However, it is still not known whether this place would comprise of worldly aspects like trees, buildings, people, towns, etc.
In other news, Tetsuya Nomura had previously stated that the game will feature a reworked battle system. The advancement of technology and modern hardware has enabled the developers to bring about a number of changes to the battle system of the game. It is Nomura himself who has come up with the ideas for these changes.
Nomura also revealed that the developers are making use of Unreal Engine to create the game. He pointed out that the powerful game engine enabled them to make the game better and more advanced in every way.
Though nothing has been confirmed by Square Enix, it is being speculated that Kingdom Hearts 3 will be released for PlayStation 4 and Xbox One sometime in 2017.
Stay tuned for more update on Kingdom Hearts 3.