Final Fantasy XIV: A Realm Reborn because Square-Enix stated it wouldn't be able to tie into the game's cross-platform servers, which allow PC players to play with PlayStation 3 and PlayStation 4 players.
According to director Naoki Yoshida, "If we published to Xbox One right now, it would essentially be an Xbox only community. An MMO is built on its community, and if it's weak, then what is the point?"
Yoshida is still keeping the Xbox One version a possibility, stating he'd "like to keep that option open" and "we want this game on as many systems as possible and get the game into the hands of as many players as possible, so we won't say that we won't do it."
He went on to note "in Japan, the Xbox is not as popular as it is in America, and maybe you only have a few thousand people who maybe really love Final Fantasy and are playing the Xbox version. But because it's a closed community, you only have this tiny community that is not allowed to play with the rest of the world, and you worry how you're going to retain that community."
Final Fantasy XIV: A Realm Reborn will be released on the 14th August 2013 on PC and PlayStation 3, while the PlayStation 4 version will come sometime in 2014.