As hinted in recent interviews with Tetsuya Nomura, it has finally been confirmed that 'Classic Kingdom', the mini-game that has been teased for 'Kingdom Hearts III', will finally be making its appearance in 'Kingdom Hearts Union X [Cross]' with the release of version 3.0.0 to commemorate the game's third anniversary. This update will be available in Japan on September 6th (no word on when the international version will be released).
In addition to the arrival of the 'Classic Kingdom' mini-game, it has also been revealed that for a limited time, those who complete a certain high score with the mini-game in 'Union X [Cross]' will receive the Starlight Keyblade from the mobile game in 'Kingdom Hearts III'!
Lastly, to commemorate this news, Tetsuya Nomura himself left a message for fans which you can check out below (rough translation / will provide a better translation once available):
UPDATE 9/5: The Starlight promotion has been confirmed for the global version of the game in a Square Enix Twitch stream today! No date has been given, but it will be coming west soon! Players simply need to achieve a high score threshold to obtain the Keyblade; it isn't a competition like other events in the game.
'Classic Kingdom' Mini-Game from KH3 Coming to 'Union X [Cross]' with Version 3.0.0