Official Blizzard Quote:
We're targeting the middle of next week for these Free Character Migrations to become available, and they'll remain open for approximately one week, or until a destination realm fills up. If you're looking to transfer with others we recommend setting up plans early to avoid any stragglers being left behind.
Area 52 => Turalyon
Stormrage => Turalyon
Tichondrius => Blackrock
Illidan => Blackrock
Bleeding Hollow => Korgath
Darkspear => Korgath
The transfers will be announced on the front page once available