Guild members who decide to relocate with their guild may initiate their own paid character transfer. Upon a successful transfer they will automatically be part of the guild when they first log into the new realm. Their guild rank and guild reputation will be intact.
Guild leaders who do not want a change of scenery may also choose to pick a new guild name using another new service. These services are in development and we will be providing additional details at a future point in time.
As with all of the features and services we offer, we intend to incorporate the guild relocation service in a way that will not disrupt the game play experience. Please note that this feature will require extensive internal testing, so you may see bits and pieces of the service appear on the public test realms. We'll announce further details at http://eu.battle.net/wow/en/