During a X/Twitter exchange yesterday, voice actor Zach Pokres let it slip that one of the projects he has worked on recently was none other than 'Kingdom Hearts IV' (which he disclosed he had permission to mention without further detail):

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It is currently unknown what role Zach Pokres is playing in the game, as it can either be a major role or simply voicing NPCs. Regardless, with the recent new screenshots that were released, and the fact that English voice acting is already being done for the game, the chances of seeing much more of the game soon seems very high.

EDIT: It appears the actor in question has deleted the Tweet. Reasons are unknown, as no comments have been made by the actor, but there's a good chance Square-Enix/Disney retracted their permission to allow Zach to mention KH4. Either way, for proof of the Tweet, please check out the video below: