Patch 4.0.1 has come and gone, and we can now use the benefit of hindsight to see how well our predictions did. I'm going to start off with the elephants in the room: alchemy transmutes and addons.
I reported that the cooldown for epic gems had been removed in the PTR and that this was likely so that people wouldn't be put into the poorhouse by having to regem. In reality, the datamining that determined this was incorrect, and the cooldowns are now resetting at midnight instead of the old way. There's huge demand for epic and rare cut and raw gems now, and people are tending to go toward rares because the epics are just too expensive.