World of Warcraft's Creative Director Alex Afrasiabi has confirmed via Twitter that the next alpha build will shut down the Horde lines in Frostfire Ridge and open up Shadowmoon Valley in its place.
Shadowmoon Valley available next alpha build with the new intro tier garrison. Horde will be turned off for this phase. Soon (tm).- Alex Afrasiabi (@Abrosiabi) June 11, 2014
Having played through a bit of the Alliance quests at the Temple of Karabor during BlizzCon, I'm particularly interested to hear what the alpha-testers have to say about the rest of the zone, as well as how the blue garrison quests are both different and similar to the red ones.