According to a report from VG Leaks, Square-Enix is currently co-developing "Final Fantasy Versus XIII," renamed to "Final Fantasy XV," (something I can't explain, but there's a history of interesting numerical re-names with that franchise) with Sony, making it a PS4 exclusive.
Confused yet? Me too.
Evidently the switch happened somewhere along the lines of the brainfart that was the PS3 launch of "Final Fantasy XIV." Y'know, the one that never happened. Until "A Realm Reborn" came out three years later. Kind of like an early, but worse version of the "Skyrim" DLC episode.
As VG Leaks explains it:
"Square-Enix announced 'Final Fantasy Versus XIII' years ago and the game was lost in the limbo. Square decided to halt Versus PS3 development two years ago, but the RPG wasn't cancelled, why? Two years ago, Square-Enix moved the game to PS4 and Sony got in the project."
VG Leaks isn't saying how they know this, where, or who they got it from, saying, "We hinted this PS4 exclusive one month ago, but we couldn't speak freely about this topic," so it's best to take this with a grain of salt until Sony or Square-Enix say otherwise.