To celebrate its 600th issue, Dengeki Playstation conducted an interview with Kingdom Hearts director, Tetsuya Nomura, who drew the artwork below for the issue's cover:

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As for the interview itself, a couple of details have been leaked (a fully translated interview will be posted as soon as it's available), which can be read below:

• There is a congratulatory message regarding the overlap of issue #600 and the announcement of KH2.8.
• The king (presumably King Mickey) and the others were drawn beforehand for the sake of expediting the schedule, but now they're being recolored to create a sense of unity.
• They've depicted this on the front cover several times.

KH3

• The “Lost Master” is discussed in X[chi], but it will be used in KH3
• The creation of Xehanort's keyblade will be discussed in X[chi] and will tie into KH3
• Kingdom Hearts itself will also be discussed further, more than the series has so far
• D23 (November 3rd) will feature a “theater” concept, so Nomura is hoping we're looking forward to the video!

2.8 Final Chapter Prologue

• The part of KH3D that explains the 7 lights and 13 darknesses will be carried on through the end of KH3
• Since “Keyblade Master” is a special title, what's necessary to become one will be taught
• BBS 0.2 and KH1-2's stories will be linked together
• Chirithy is the one speaking in X[chi]: Back Cover

Unchained X[chi]

• Chirithy is the player's guide
• The “Master of Masters” is the teacher of the six apprentices, and it will be revealed in X[chi]: Back Cover who the traitor is

Special thanks to @libregkd for the find.

Source: NeoGAF & KH13.com