For what it's worth I think these are pretty good looking miniatures- I don't play The Old World (though in our group we still play in the old world, just using a combination of homemade, out of print, and other games' rules), and as our campaign has ranged to many locations, it's not inconceivable that someone would end up in Cathay or running into Cathayan forces.
That said, while I'm sure the price tag on these would make buying an army a bit of a stretch, the thing that will probably keep me from indulging in a small number of models is likely the scale. Generally I'm not a stickler for scale, and I incorporate a good number of oversized Reaper minis alongside smaller NorthStar and older Warhammer guys, but for some reason I feel like having a whole unit of seven-foot swordsmen or something would feel like too much.
I'm tempted to get the book, just to see how or if they are able to blend the Celestial Dragon Emperor bit into the existing lore in a way that makes some sense. Of course we've generally had more fun making up our own branches of the Warhammer World, so there's that issue of "it's hard to unread something," especially if it contradicts something you've enjoyed. Case in point, I found the map of Albion in the "Storm Warriors" book to be way cooler than the Albion campaign setting map which felt kind of flat. We got around this by saying both of those maps were in world, and both wildly inaccurate, but I'd hope they find a way to tie in the lore that feels like it fits.
Anyway... we'll see how the minis look once they're out. Wargames Atlantic is doing a Warring States Chinese army that will likely make a cheaper (and closer to 28mm) alternative.