I think you guys are all getting a little too worked up over this.
For one thing, its not like China is chasing a static target. China-bashers love to mention the very first year an engine was introduced, but they either cannot comprehend, or are wilfully ignoring the glaringly obvious facts that the AL31s and F100/F110 etc of today are vastly improved compared to their first irritations from the 70s to the point of almost being entirely different beasts.
The latest AL31s the WS10A has to compete with only came out a few years ago and/or are still in the final stages of development.
The very fact that most of the PLA new built J11s and other Flanker derivatives are using WS10A is a massive deal, and is proof positive that Chinese engine development has come of age.
The other pair major factors that people seems to forgot is that a) engines take a very long time to develop and mature, and that b) we as outsiders can only view progress in a very rudimentary binary form - either an engine is ready and in operational deployment, or its not (well technically we get the odd rumour, but since they cannot be substantiated, I have disregarded them since it cannot be taken as conclusive evidence no matter how good the reputation of the person putting out the rumour, I do give them the attention they deserve, but that's a judgement thing).
We cannot see the progress that is being made on the very long road from no engine to having operational engines, so for years, just because we might not seen any evidence of progress does not mean progress is not being made.
The very fact that there is a WS15 in advanced development is massive progress compare to only a decade ago.
Now, not only does China have its own indigenous high performance turbofan in operational deployment that is comparable to other engines of its class anywhere in the world, it is well on its way to developing an example of the very best engine class currently available anywhere, and will be only the second or 3rd member of that very exclusive club depending on how the Russians fair with their engine.
Now, back on topic, I actually view the "rudimentary" mating of the engine nacelles and engine as well as the lack of treatment of the AL31s heartening.
Its not that CAC isn't capable of adding the fine finishing touches or simply forgot (the did all of that with the earlier prototypes after all), but rather that they are not bothering. And the only plausible reason I can think of as to why they would not bother with all those final details is if they know or expect to be changing to a different engine eventually, so would rather design the nacelles to fit the new, ultimately intended engine perfectly and live with some gaps or other slight blemishes while the J20 uses its current stand-in engine, so that when ready, then new engines could slot in with minimal effort and modifications necessary.
If there was ever any doubt that the AL31s would only be a temporary interim stand-in, I think this should put those doubts to rest.
The fact that the J20's current engines are only stand-ins would also be a key reason for why they are not bothering with WS10As.
Just what would be the point in wasting time and money adapting a second interim engine that would ultimately only need to be replaced once the WS15 is ready anyways?
As such, I don't think WS10s were ever realistically on the table. Once the J20 gets an engine change, it will most likely be WS15s, but we are several years too early for that based on the best estimate I can get from piecing together all the rumours.
In all likelihood, if this is the block 1 LRP standard, the first regiments of J20s will fly with AL31s. It will probably be the second or third batch of serial production planes that will get the WS15, and that's probably being optimistic and assuming they don't run into any unexpected delays with the WS15 development.
