Well maya said high altitude core testing or something like that has been completed (he said this a year or 2 ago). Is it actually used in one of the J-20 prototypes? I strongly doubt it. I am in the AL-31FM# variant club when comes to J-20 engines. Let the WS-15 take its sweet time. Let it mature. Even the PAK-FA won't have the 5th gen engine until the next iteration....
Then WS-15 has already flown ?