Bungie announced today that Destiny will be going offline temporarily tomorrow as part of a scheduled server maintenance.
Maintenance is expected to begin tomorrow at 8:00am PDT (11:00am EDT) and is expected to conclude around 12:00pm PDT (3:00pm EDT). Of course, it's just as likely to be delayed or wrap up early. But the four-or-so hours, you will not be able to log into Destiny. Should you be playing the game, you'll receive an in-game message prior to maintenance beginning.
If you attempt to login during maintenance your console will explode. Well, not really, but you may see the error code "Loganberry".
Bungie didn't clarify beyond "server maintenance," but it's possible some of the work being done could be in preparation for The Taken King expansion, which launches next month. Speaking of The Taken King (see what I did there?), Bungie released a new trailer for it today. Check it out above.