From WoW blog community:
-Not available at the beginning of Patch 5.0.4The first two Scenarios (one for Horde and one for Alliance) are coming with 5.0.4, but they won’t be enabled until a few weeks before the Mists of Pandaria expansion release. Keep an eye on the front page of this blog for more info.
-It's just a scenario ? Not a world event ?
I expected better. There is really a joke. Where a you imagination Blizzard ?