Holy mackerel. If this is true, it would be absolutely be sensational. Looks like a convergence of plans? New WS15 engine on new fighter jets and additional carriers to land on. The pilot training must be in a frenzy.
I can only agree with @Intrepid ... even we all know how such big news are unveiled in China, and there is a high chance of being true that there's a second CATOBAR carrier under construction at Dalian, there so far is still NOTHING confirmed.
And how you come to the conclusion that this rumour is related to the WS-15 - which in fact is nowhere mentioned in any recent romours especially related to a 4th carrier - is beyond me. Quite to the contrary, there are in fact even NO recent rumours suggesting a navalised carrier-capable J-20 powered by WS-15 will appear anytime.
IMO we should all calm down, sit and wait, drink some good Chinese tea ... drink maybe even more until a module was spotted and only then I would say this rumour became a fact. All other speculations are nothing more than fan-boy's wet dreams.
Best,
Deino