Let's just put it this way: if there is a need for the J-15, then the J-XY would do a far better job of meeting that need. If there is zero need for a J-XY, then there is no need for newer J-15s.Well that may be true, my argument is if you think in PLAN's shoes, J-XY is not necessary an urgent need, but a nice-to-have. CV-17 is not going to be used to invade the US west coast. All the potential targets for China's carrier fleet can be handled well within the capabilities of J-15. So from the risk point of view, upgrade the J-15 is much lower and therefore more valuable than making all new J-XY immediately. I'd rather see them spend more time on J-XY, especially the engine.
Once the Navy makes an explicit announcement, or we see the actual J-XY plane, we will know better. For now we can speculate but nothing is firm.