Blades are made in production runs, probably a few hundred to a few thousand at a time. Probably even tens of thousands for the really inexpensive and popular models (like the M8). So they ship out maybe a couple thousand immediately and store the rest to fill orders in the future, and may not make the same blade again for several years. So many blades never actually "go out of production" - if enough orders come in and stocks run out they might deem it worthwhile to have another production run. To start another run a lot needs to be done - materials must be ordered, time slots on tools must be freed up, tooling - jigs, etc. need to be assembled (I suppose these days they'd have to find the files to reprogram the CNC routers). They might decide to make changes to the blade - update the handles, change the silk-screening, maybe even change the materials if they can't get their hands on what was used in the past. For this reason a long time may elapse between running out of a specific blade and when a new production run can start. They won't make more unless there are significant orders in the pipeline.
And then there are blades that aren't that popular - the retailers don't get many orders in, and they'll decide not to order any more once they've run out. The manufacturer still has two or three hundred in the warehouse, but no orders come in so they sit there for a few years. But then someone calls in and asks if they can "special order" ONE blade, and the email will go from the retailer to the manufacturer, who has to retrieve ONE blade from the manufacturer's store room (it's in a pallet along the back wall, and someone has to go in there with a forklift, move a lot of other pallets out of the way, and look at hundreds of boxes before they find the right boxes). This one blade eventually makes its way to the customer (it might take 2-3 months). Eventually the manufacturer decides to clear the warehouse of really old stuff and puts lots of it on sale to distributors at low prices, and after that, there aren't any left in the warehouse (maybe they'll keep 2-3 dozen just in case). And then they drop the blade altogether from their catalog (their special catalog that goes to their distributors, that is), which means it really IS out of production. The only way more get made is if a large distributor with long memory (and old catalogs) puts in a big order, in which case all the jigs, production notes, etc. need to be dusted off before another production run can start.
So who knows what the true status of the Hao Shuai blade is - the thing to do is find the 729 dealer in your country and try to special order the blade (get two or three while you are at it, and specify matching weights if available). If there are still a couple dozen in storage in Tianjin, you'll be able to get your hands on two or three. If they're all gone, your only hope would be if there are enough accumulated orders for 729 to justify another production run, which might happen in 2-3 years. There may be the odd blade in stock here and there around the world, of course.. and I doubt 729 would have a system where they can send an email to all their distributors asking if anyone has a specific blade in stock..
I got my Yinhe Kiso 7 blade by special order from Yinhe (through Tenryu) in this manner. They're practically out of stock everywhere you look but there may be 2 or 3 dozen in storage at Yinhe. What was funny was they actually laser-engraved "MALAYSIA" on mine..
Took 2 or 3 months to arrive.
Iskandar