Oceanic realignment.

Blizzard will be opening up free transfers from high-population Oceanic servers on December 27th, so if you're sick of your population issues, think about jumping ship. Here are the affected realms:

Source Group A (PvP)
Barthilas
Frostmourne
Jubei'Thos

Destination Realm A (PvP)
Thaurissan

Source Group B (PvE)
Nagrand
Aman'Thul
Dath'Remar

Destination Realm B (PvE)
Caelestrasz*

You can find all the details at the official forums.