Machine Zone and Square Enix announced the release of a smartphone version FINAL FANTASY XV MMORPG game based on the upcoming FF XV PS4 / Xbox One game.
It has been announced via the Machine Zone press release and the two companies working together on it!

Machine Zone is the developer of the Game of War and the Mobile Strike so it is a well known developer company. Square Enix and Machine Zone will release more information in the near future. If we have to guess, the game going to release in 2017 Spring / Summer.