Thats the thing with stealth aircraft if not with just any kind of platform. You need to be able to achieve economies of scale and buy dozens of these aircraft to reach any employable operational rate. Buying just a peacemeal quantity may not only jeopardize the operational rate/costs like the B2, but also may hamper complete integration into the strike force order of battle of these platforms.
As far as i see, any new non stealth platform entering service now will have a hard time maintaining its mission success rates within just a decade from now considering proliferation of A2/AD systems around the world.
You do, therefore, need to start manuevering your strike force towards platforms that have a certain passive capability to work around those denial systems. USAF too is having a hard time thinking how they are going to operate with non stealth tankers like the 46 Pegasus in the future.
USN may mitigate this to a certain extent by using Mq25 and F35 in conjunction.
The PLA's present procurement today is made in mind with an understanding of current technology availability and current/foreseeable threat profiles, while balancing what future technology they will have and future threat profiles.
It's all well to say that non-stealthy bombers are outdated trucks and that future bomber fleets should be fully stealthy, but it will take many years to achieve that. For the PLA, it will obviously take a number of years until they reach a relevant number of H-20s.
In the interim, should the PLA and other air forces simply ditch their non-stealthy bombers? Do modern non-stealthy bombers offer no relevant capabilities in medium or high intensity environments at all? Should nations simply retire those aircraft and wait for years until stealthy bombers arrive?
Or, do you keep those non-stealthy bombers in service and upgrade them with new self defense systems and more importantly give them new, longer ranged weapons to have a chance at striking even defended targets at standoff distances, and gradually phase them out as your new stealthy bombers enter service?
Cause that is what basically the US, Russia and China are doing.
For China specifically, I think they will continue H-6 variant production for a few more years before finishing it up. H-6K/J/N variants still offer some capability that other aircraft do not have, and while they may not be survivable in certain circumstances in a high intensity environment, they can still be relevant if adequately upgraded with new weapons in time. They are also likely relatively cheap, reliable, and offer regional ranged strike capabilities to supplement the PLA's other regional strike capabilities as well, even if they only operate from within Chinese air space.