I could be wrong here, but I'm fairly sure I remember seeing that the new Hard Mode dungeons would be dropping ilevel 70 gear because the Myth cap was going to be lifted, and the other tomes were going to be used to cash in for the Myth tomes or the new ones that we were going to be getting. In essence, if you're doing the ilevel 60 dungeons, you're going to be wasting your time because there will be several dungeons that will be giving ilevel 70 equipment.
I didn't find the right solution from the Internet.