Square Enix has done an excellent job keeping Final Fantasy XV relevant post-launch, particularly as of late. Between the character DLC for Gladio and Prompto, as well as the still unreleased Ignis pack, there's been plenty to keep fans busy. And with the announcement that the game is coming to PC, the game's player is on its way to getting even bigger.
That said, Square Enix will have to start thinking about moving beyond Final Fantasy XV at some point, especially with its one year anniversary coming up in a few months. As a single-player RPG, it's difficult to keep a game like this interesting when most players are done after completing the 40-hour story mode. Game Director Hajime Tabata told IGN that the time is coming for when the team needs to start looking beyond the game at what's next.
He said:
"At the end of the year, I think we do have to have a drawing of the line and moving on to do the next project as well. Obviously we’re doing a lot of different things within the XV development team at the moment. But every single thing that we’re doing then really is something that we have to do to get the experience to move on to do our next project. So I think we will clearly be moving in that direction at the beginning of next year."
Tabata also references how taking Final Fantasy XV in "different directions" is preparing them for that next project, though what exactly that is, remains to be seen. One thing that we can pretty much rule out is a direct sequel to the game, so it's possible that Final Fantasy XVI could be it. At this point, who knows.
With the Final Fantasy VII Remake and Kingdom Hearts III still in active development, it doesn't seem like a potential sixteenth entry in the Final Fantasy saga would be anywhere near ready to go until the 2020's, so it could be a while before Tabata and Co. are ready to show off what's next.
Source: [IGN]