The following announcement came from Blizzard today regarding Realm transfers.

Realm Transfers
The following realm transfers are being temporarily disabled:
Blackhand to Windrunner
Warsong to Bonechewer
Whisperwind to Azjol-Nerub
Blackrock to Daggerspine
Arthas to Nathrezim
Bleeding Hollow to Crushridge
Illidan to Stonemaul
Stormreaver to Stormscale

We apologize for the short notice and we hope to have transfers available to these two realms active again in the near future. Please check back here for future updates.