Ommra from Blizzard EU chimes in with a bit of information, have a listen...
The Burning Crusade is soon upon us and in preparation for launch we’re continuing to make sure the population on the realms is at a level where the community thrives and queues are not overly long and/or frequent. There are several measures to ensure this:
Realm tags: the “Full” and “Recommended” realm tags will be used continually to direct new and restarting players where to start new characters.
Free migration: we’re currently preparing a batch of free migrations. Read more about it
here. Additional free migration may be run after launch.
Raising realm caps: as the increased world size naturally accommodates for more players online all realms will have the population caps raised at launch.
New realms: at launch we will open a number of new realms. The exact number and names will be revealed soon. More realms will be opened as needed in the weeks and months ahead.
Realm split: in the case other measures are not enough we will consider doing a realm split. You can find more information about realm splits in the
FAQ.
Thanks