Glad to know I'm not the only one who's intent on taming all Draenor wolves
As for your answer, loads of beasts who should be tameable aren't, as the huge taming pass they complete just before it goes live hasn't happened yet. There's several wolf skins that we haven't even seen in beta yet, so it's safe to assume mountain hunter won't be the only black Draenor wolf about.
The taming pass, in case you didn't know, is when Blizzard go through all beasts that they feel should be tameable and make it so. There's those terroclaws and terroclaw chicks that have been confirmed to be tameable, but the taming passes Blizzard have been doing are only small, and these aforementioned beasts aren't tameable yet. So don't panic. I know it's only 2 months and 3 days until it goes live, but they've got loads of things to still say are tameable
I've kinda avoided giving you an answer. I think it's safe to assume this wolf isn't in game yet, but there are other black wolves about. No black wolves are tameable yet, however. Unless I've missed something

It's hard to give certai answers if I'm not in the beta. Damn I wanna be in the beta...