What I'm hoping will happen:

1 day before the servers go down we'll see Dalamund in the sky, and it will slowly get bigger and bigger with a countdown timer on the screen. All the shops and guilds will be closed since, well, the world is ending. So basically we can log on and watch Dalamund get closer and closer. When the countdown hits 0, then the cutscene will play that shows Dalamund hitting Eorzea, and so no one misses out, you can log in anytime after the servers go down to view the cutscene.