There won't be. They've made changes to the game precisely in order to contain the story to just one game. And I also believe they want to move on from it and the Fabula Nova Crystallis era as quickly as possible now.
Beyond FFXV there will be the remake of FFVII and I'd wager the focus will then move onto FFXVI. I'm very much looking forward to the latter. We've been hanging onto Noctis and all the drama that his game has brought for far too many years. Even if FFXV ends up being a good game, I'll be very happy to be done with it and finally look forward to a completely brand new main game in the FF series. One we know nothing about and have no expectations whatsoever attached to it at present.








