Nether Drake

As others have said the nether drake quest line has yet to be implemented but will be in the next major content patch.

Q u o t e:
I'm not really sure why you care?

I mean, Netherdrakes are apparently intended to be as rare as the Arena's Swift Nether Drakes. Meaning there'll be about 8 every three months.

No the non-armored nether drakes are a cool alternate epic flying mount that's intended for anyone to be able to achieve through a long and difficult quest line, which won't require any raiding.

There is another mount that has yet to be discovered that is meant to be as rare as the armored swift nether drake from the arena, and offers the same additional speed increase as the armored swift nether drake.

Q u o t e:
As in, more than just a long quest difficult. If its just a quest, then in a month everyone will be riding a netherdrake.

Possibly. Don't forget you also need the epic flying mount riding skill, which I don't think everyone is all of a sudden going to be able to afford. If everyone wants to do the quest and take on the requirements needed to obtain one then they will, but I don't think it's going to be a quick 'kill 5 of these' and turn in type quest, and if I had to guess would have other requirements associated with it as well.