Square Enix Japan have announced that a new Kingdom Hearts title will be releasing for iOS and Android in 2015, known as Kingdom Hearts Unchained χ. The title will be free-to-play with optional in-app purchases, the first smartphone title in the series, and an adaption of the PC browser game Kingdom Hearts χ[chi]. We will update as more information becomes available.

Thanks go to @htmk73 for the information (original tweet below, translated by goldpanner), and to @aibo_ac7 for sharing it.