Square Enix hosted their own presentation this morning at E3 where they announced/confirmed that Final Fantasy XV will be ported to the Xbox One. FFXV was originally Final Fantasy Versus XIII, which was supposed to be a PS3 exclusive. Now that it's going to next-gen, Square Enix obviously wants to spread out the appeal to a wider audience.
In addition, the company has announced it will be porting Kingdom Hearts 3, which is a larger surprise than the news of FFXV. While KH games have gone to non-Sony handhelds before, this is the first time the series will venture to a new TV console. Considering there hasn't been a KH game this current-gen for consoles, it's not too much of a leap to think Xbox One owners will want the game on their console to avoid buying the PS4 if they had no plans to buy a PS4 in the first place.