It seems the Opening of the Gates of Ahn’Qiraj event is far more than fans realized.  According to Caydiem—Community Manager of World of Warcraft—something will happen in various locations of Azeroth around the same time the gates are opened.  No one knows for sure, but this seems to be some sort of World Event similar to that happened at the end of Open Beta where all towns and cities were attacked by waves of mobs.  This is speculation, but judge yourself by reading the message below.

Caydiem: “We’re aware that many realm communities are becoming excited as the War Effort nears completion. Several players, wanting to see the event, have created alternate characters on the realms closest to completion and have trekked out to Silithus in order to bear witness. While we respect your enthusiasm, we do need to take steps in order to allow the realm communities who have worked for this completion to be able to enjoy the fruits of their labors.

As such, we are temporarily shutting down character creation on Medivh and Mannoroth. If you have characters there already, you will be able to create new ones without a problem, but those without characters will not be able to create new avatars on these realms until the event is complete. We may implement additional measures as the situation warrants. This should hopefully cut down on the latency experienced by large crowds and allow the industrious communities of these two realms to experience the opening of the gates.

Keep in mind, also, that there’s more to see than just Silithus when the event unfolds—there’s no need to gather all in one place. Keep your eyes and ears out for events around the world!”