From what I'm aware of, we have a policy regarding the placement of the hearts from Template:Game on articles for content from games that have yet to be released. However, due to the eagerness of some new users, the hearts have been unceremoniously added and subsequently removed a few times now.
I, for one, think that we SHOULD add the hearts to some articles we have confirmation for. On the Kingdom Hearts III page, in the story section, we have a statement from KH3's press release: "Believing light and darkness must remain in balance, Master Xehanort seeks to spark war against the ‘tyranny of light’ to restore equilibrium. In an effort to undermine Xehanort’s plot, Sora, Donald and Goofy search for seven guardians of light and the “Key to Return Hearts,” while King Mickey and Riku search for previous Keyblade wielders.". This statement alone confirms six characters to appear, and we have more interview statements from the references as well, so it wouldn't be entirely unreasonable to add the hearts to some pages. Rex Ronald Rilander (talk) 04:26, 3 October 2016 (UTC)