The cost might be an issue, but as long as PLAN has the ambition to conduct any combat far away from the land-based aero support, I don't think it will stop them thinking about the 5th fighterAgreed.
How many J-XY jets would actually be needed?
With an additional 2-4 carriers in the next 15 years - call it up to 150 new fighter jets would be needed.
If you were to begin an entirely new programme, a small production run of 150 jets means:
1. the upfront development costs are going to be really high, in comparison to the production costs
2. the production costs are going to be high because of the small production run.
2. the production run will also begin and finish quickly
I don't see that as being enough aircraft to justify an entirely new programme, since UCAVs will likely be part of the airwing as well, and they already have the J-15.
So for the 003 carrier, I reckon they'll fill it with newer catapult-capable J-15s.
Then for the 004 carrier, stealth UCAVs may be ready in the 2025 timeframe, so production switches to this.
Then the 003 and 004 airwings are reshuffled to be mixed J-15/UCAV.
The technical requirements for carrier and land-based UCAVs are similar enough that you could have a common programme or subsystems to achieve greater scale.