I'm not sure if you accounted for this in your calculations, but you have to remember about customization too. There are I think between 8-12 different faces, which really is only the skinning, I'd say perhaps 10 or so hairstyles that would need to be rigged, although since they use the hairstyles across races lots of them just need tweaking, rather than completely redone, and then there are the features. It's one thing for certain races to have features like hair colour, earrings, or even facial tattoos/colouring. But look at troll tusks and tauren horns, draenei tentacles, dwarven beards, etc.
So it could be a bit longer than you've mentioned, or you could be considering those factors when you gave those estimations. I think the important thing to take away is that Blizzard hadn't been actively working on the models, because they were a low-priority project. When they decided to do them instead of race/class for WoD, they got prioritized and are proceeding much faster. That's why they said they were "25% done" after three years a few months back, but are now clearly in the final iterative state for male gnomes, dwarves and orcs, and maybe 1-2 iterations on male tauren, female gnomes and female dwarves. Based on the teaser trailer, I'd say they're quite close on female draenei as well. Hilariously humans are probably fairly far back, even though they skin all the armor onto human males first, and then adapt it for the other races afterwards.
I think they've given themselves leeway by saying they might release the models after launch, but I wouldn't be surprised if only a few races, or even none at all were not finished for launch. Plus I think they funneled some of the normal boss art budget into Orcs, since Garrosh was a final boss and people would've cried if he was the generic orc model he had before. Nobody wants to fight low-poly bosses in this day and age. That's why the orc male is already ready to go.
As an aside they are also rigging cloaks now, which is friggin' amazing and one of my major graphics complaints about WoW over the years. And they're working on the clipping of hair and armor apparently as well.