Despite plans on avoiding a day one patch, Final Fantasy XVI will indeed have a day one patch when it launches in the next few days.
This information was confirmed via their pre-release livestream, which shared lots of new information for the game.
Game producer Naoki Yoshida (via @Genki_JPN) said the patch will mainly consist of performance optimization and bug fixes. While there will be a day one patch, it is not required for users to download it in order to play the game.
They apologize for failing to keep their initial plans, though depending on the size of the update, it may not bother anyone at all even if the concept of day one patches have usually been a sign of rushed development for the sake of hitting a deadline.
Whatever may be lost out on an unpatched version of the game doesn’t seem to be bothering those who managed to secure an early copy ahead of the game’s launch. Square Enix asked owners of leaked copies to not to share gameplay ahead of launch and will DMCA anything that does get posted until then.