There's still three weeks until expansion release, plenty of time. I don't remember the last time reveal season began more then three weeks before release. It usually lasts two weeks, sometimes even less. We'll probably hear something later this week.
if i'm not mistaken They revealed darkmoon faire cards at the 3rd of november expansion released at the 17th, so assuming the expansion drops at the 23rd, reveals should start at the 9th, as someone mentioned above
The issue with the "two weeks of reveals" math is that almost every time there is a week between the final reveal and launch. as stated it's to draw in pre-orders. sometimes it's as much as two weeks. so them not starting until two weeks before launch means that they have 1 week to dump all the reveals and 1 week to wait for the cash to flow.
Now obviously that is a generalization. we are talking about the team that at Blizzcon once said "There's a new expansion coming out Thursday, Surprise!" so they could be purposely shaking things up, as they like to do.