Elder Scrolls Online is ending, and as such the team has taken both of the megaservers offline in preparation for launch day tomorrow. The downtime for the game, store, and account services is estimated at a few hours.
Once ZeniMax plugs everything back in, players will see a few big changes in the game's store. The updated store will offer subscription billing, upgrades to the Digital Imperial Edition, and the Palomino horse mount. In-game mail will also be restored.
[Thanks to Space Cobra for the tip!]
[Update: The game is back up and ZeniMax has officially declared it a launch!]