Nostalrius Begins - Quality wow vanilla realm (1.12)

According to Viper's Post:

Dire Maul will open 1 month after Molten Core & Onyxia Lair content is cleared.
Regarding raids, Black Wing Lair will be available 2 months after Molten Core & Onyxia Lair content is cleared.

So for the people who cleared MC and Onyxia already, they'll be waiting for quite some time

But it gives nascent guilds to finish the content along with the ones who've already done it.

According to timeline DM should be about 2 weeks away and BWL should be 6 weeks away.