What exactly you think they need to prepare?
The server was not damaged.
All the systems are in place and just need to be booted up, so realisticly it does not need to take much longer than a normal maintence (about an hour) after the server is up again.
Of course they might have planed an event or some form of "compensation" for down time which could take time to implement. But hopefully they will just open the server up while they work on this event and implement it when it's ready and make an extra server maintence.