Um... Deino, China has been using PL-17 missiles in PLAAF for a long, long time.
When it's confirmed in our level, it is not only old, it has already been superseded. PL-17's replacement level missile is surely in PLAAF service.
Basically PL-15s superior is the PL-16 which is thinner and likely an improvement in all parameters. PL-15 is now an ancient missile to China. It is used for practise so they can be expended.
PL-17 is the long range missile. Its replacement has been around for some time according to Chinese forum discussions. There is also another type of missile that outranges PL-17 and PL-17's replacement.
So basically think of PL-12 as beyond ancient. PL-15 is ancient.
PL-16 is standard "mid range". These days mid range = previous years ultra long range due to new energetics, optimised guidance and trajectory computing, new generations of rocket engines, better throttle control and energy (fuel) management, better materials, better aerodynamics. Also tricks like dual or n-pulse controlled rocket motors (can control how many times your engine switches on, how long for, how much force it gives your missile) which open up entire new dimensions of movement optimisation. PL-16's replacement is around. This is how old PL-15 is.
PL-17 is standard "long range" and has been around more than 10 years since J-16 shown to you all flying with it. When it was shown, it would be old. Nothing new is ever exposed. I repeat, nothing novel and new is EVER shown to the internet. Whatever we see online is older than old. Please reverse this whole philosophy of confirming things with official announcement and only when serial numbers are counted. When those happen, these things are boring old stuff.
PL-17's replacement is said on Chinese internet to have been around for some time now. They are not ready to show it at all though. Even PL-17 is rarely shown these days but every few times a year we get a few photos.
In China, every 2 years is a new generation of car. Legacy automakers average is 6 to 8 years per generation of car. 3 or 4 years for a mid life upgrade for the car model. China used to also do that with MLU around 1 year or 2 years. Now it's entire new generation in 2 to 3 years. With missiles and military technology, it is about the same cutthroat iteration pace. Old generations are kept around with some manufacturing capacity left for them for redundancy. Really old stock are completely fired off and tested, intercepted etc.
PL-17 to PAF is not going to be some surprise or remarkable thing. If the business and politics makes sense, it would be easily, too easily done tomorrow. The question is the politics and business. PL-17 is not some safe queen for China. It's from mid 2010 or much earlier.