Starcraft 1 got delayed like 2 years back when the company was barely a few years young and their developers had to work overtime and sleep at the office just to release the finished product....2 years later, when they didn't have billions in the bank to spend on dumb TV shows and developer time creating pokemon for the game.
Now I'm hearing about zones at release not having content, flying getting removed (because of not wanting to put in the work to make it a more challenging and dangerous feature of the game), not all races having their models redone, some of those redone still having reasonable doubt surrounding whether they will be completed properly or not, Ashran apparently being a pointless mess, art being reused all over the place.
Sounds to me like this expansion will more likely be rushed than released "when it's done". You don't start cutting away features from your game and copy pasting and then pretending you're all cool with that or whatever, that you took every measure to put everything in. WoD is obviously far from "done".