Many communities have been linking to our Netherdrake page where I speculated there would be a Netherdrake mount obtained via PvE-reward through reputation. Blizzard just confirmed this.
Drysc: The armored Netherdrake will be available through the arenas as a reward, and a Netherdrake that has a distinctly different appearance from the armored Netherdrake will be available through a quest line which has not yet been implemented. It’s likely that it will be implemented with the next major content patch.
They’re both epic flying mounts, just to clear up any confusion on their speed.
As far as I’m aware the current plan is to make them both the same speed, which I believe is planned for 310%, a bit faster than the purchasable epic flying mounts. That’s of course subject to change.
Source: Wow Forums