I did not report on this the first time because it did not seem like a credible rumor. As it turns out, they were citing an interview with the game's director from Famitsu, the Japanese video game magazine. Basically, while Square likes to make their own engine to use with their RPG projects, their Luminous Engine did not satisfy their needs so they decided to shift production to Unreal Engine 4. While it is still not scheduled to come to the PC, we know that the engine feels at home on our platform.
Image Credit: Wikipedia
It seems pretty clear that Kingdom Hearts was not moved to Unreal Engine 4 for PC support. That would just be silly. More likely, their internal engine might have needed a little extra development work and, especially with the vastly different art styles of Kingdom Hearts and Final Fantasy, they moved the two release dates further apart. Maybe they will even release Kingdom Hearts 3 earlier than intended?
But, if it does come to the PC, it seems somewhat more likely that it will function better than Final Fantasy XIII does. That title was locked to 720p with a few odd quirks, like Esc being the equivalent of "/qq" despite even Alt+F4 giving a warning prompt, and that it seems to require a keyboard to close (I could not find a way to close the game with the gamepad or mouse alone). That said, while a tangent-to-a-tangent, I did like the option to have the original, Japanese dub. Yet again, I digress.
This was not the first time that Square has developed an RPG on Unreal Engine. The Last Remnant, for the Xbox 360 and PC, was developed on Unreal Engine 3. Kingdom Hearts 3 does not have a release date, but it might be sooner than we expect (and probably much earlier than Final Fantasy XV).