As everyone else has pointed out, Square has specifically said that FFXIV isn't on Xbox One because Microsoft won't allow cross-server play with PlayStation. As seen with recent announcement of Dragon Quest X on PS4, we can likely guess that cross-play between PlayStation platforms and Nintendo platforms isn't as big a deal.
While this is only one game for the time being, I can only see this hurting Xbox One in the long run, especially if the gap between PS4 and Xbox One continues to grow. In the medium-term, I can see this policy preventing XB1 from getting a game like Rocket League. But further down the line, I can see developers that make MMOs pushing for PS4 and PC cross-play as opposed to separate servers for PS4, PC, and Xbox One, since maintaining a strong, single user base is essential to those types of games.