The Final Fantasy XV trailer has a tagline at the end of it that says "a world of the Versus epic." During the Future of Final Fantasy press conference, Siliconera asked Shinji Hashimoto if that meant Final Fantasy XV will have direct sequels like Final Fantasy XIII.
Hashimoto replied that Final Fantasy XV is a large scale game and many stories may come at a later time.
Square Enix is certainly preparing for future Final Fantasy XV stories considering they filed a trademark for "A World of the Versus Epic." Final Fantasy fansite FF-Reunion spotted the trademark, which was registered in Europe by Square Enix Japan.