I understand these sort of projects take time. As an aspiring game developer, I often side with Blizzard on many of their arguments, because I can see both sides of the fence, and often enough they're right.
What is alarming though is the fact that they've said they're at a stable 25% with the models which gives the indication they won't be ready for the next expansion. I've no doubt Blizzard could pull it out of the bag if they wanted, but we've still yet to hear they're really committed to getting them done, as we're always told; "They're on the wishlist".
I'm glad they're taking their time with this project, but 25% was alarming to me. I just hope they pull it off.