It's pretty apparent to everyone that the current drought of content in WoW is going to be the longest since the game began.
It's rather interesting in light of how the expansion began. The first few patches came really fast. Almost too fast, in my opinion. Blizzard could have easily added another month to each of 6.1, 6.2 and 6.3. That would have spread out the content better.
But they didn't. At that point in time, Blizzard obviously believed that they would hit the deadline for the faster schedule. So I wonder what changed.
My theory is that they had to scrap a lot of already designed work and restart at some point. Maybe it wasn't up to their standards, or just wasn't working out.
Another possibility is that they wanted to make significant technical changes (perhaps the change to the new file format), and that ended up taking significantly longer than expected. Though I am not really certain that significant technical changes would have held up all the content generation.
I don't think, however, that Blizzard is delaying the expansion because they can, or because the "suits" felt it was the path to maximum revenue. Rather, I think something happened after the start of Mists, probably after 6.3, that made delaying the expansion the lesser of two evils.