Everything that changes in Frosthold is announced here, at two speeds: the notices you should read and the notes for whoever wants the detail.
Notices
Notes
The realm leaves the original game rates behind: x8 experience, x4 items, x4 professions and x8 reputation. Quest gold is untouched.
Read the entryIt downloads the full client, checks every file against its hash and leaves the realm configured. Windows for now.
Read the entryFrosthold goes live with phase 1: Naxxramas, the Obsidian Sanctum and the Eye of Eternity.
Read the entryWhat opens next, and when, is in the phase plan, and whether the realm is online right now is answered by Status.