It seems to be pretty important and hefty.
In spite of Square Enix’s promises about Final Fantasy 15 shipping complete on the disc day one (this was, after all, the reason that they gave for delaying the game from its original September 30 release date), it looks like the game will still have a rather hefty 7.7GB patch right on the first day itself, after all.
And what will the patch entail? Will it at least be largely inessential stuff, so that the game can still be enjoyed in all of its glory by people whose internet connections may be poor? In my opinion, no- it looks like the update will be adding some rather important features and functionality to the final game that should have been there in the base game.
The presence of this patch indicates to me that there was more to the last minute delay for Final Fantasy 15 than Square Enix let on- which is right, I suppose, developers don’t always share the full nitty gritty of game development with their audiences after all. You can check the full details of the patch below. Final Fantasy 15 launches on PS4 and Xbox One on November 29.