Cathay has been revealed for WH3 and with it comes a bunch of retcons, as to be expected.

The Dragon Emperor is know confirmed to be an actually dragon, and not just any dragon. He and his consort, the Moon Empress, are immortal dragons who have always ruled Cathay (except maybe that Monkey King incident that remains unmentioned), and have been around since before the Old Ones arrived. Not only that but they are said to be as powerful as most of the gods.

So what does someone that powerful do? Apparently sit around the Celestial city all day nasal gazing. They aren't playable and instead that falls to their children, more immortal dragons who can assume human form and rule various parts of the Empire. They must have been asleep when the End Times happened as well...

GW actually stated out their units using 8th ed rules and they are described as having a stalwart, hardy frontline with incredible ranged firepower, while being slow and easy to flank. Sounds like dwarves, but unlike dwarves they also get cavalry, flying cav, dragons, giant terracotta warriors and flying Chinese lanterns with guns onboard.