The biggest deal to me is just seeing that they've frozen on the design and material already. That tells me the initial testing has been quite successful. This is a huge milestone. When WS-10 was first put into service, it really was rushed. As they started production after design certification, they were still including and updating the materials they were using. Because the original material they used in the design certification just simply wasn't meeting standards once they put it into use.
What we can see is that WS-10C already matches PLA expectations in performance and service life. So WS-15 likely will be already be relatively reliable by the time it is put into service with J-20.
And when it comes to next gen, it appears they are already far along in development. that's great to see. and by the time it goes into production, I would also expect it to be ready from design & material science point of view. That's something US/UK always had when they developed new engine and China never had until now.