The two previous Kingdom Hearts were PS2 exclusives so it doesn’t suspend disbelief to hear the third staying with the PlayStation platform.
The Official PlayStation Magazine has it listed as a PS3 resident and that it should be “announced at TGS”. Nearly three years since the last Kingdom Heart’s outing.
”Kingdom Hearts III is currently in development as a PS3 exclusive and will be announced at TGS”, reads the mag reports Kotaku.
The Tokyo Game Show starts in about a month so sit quietly and don’t fidget til then, or play some games - it’s your call.