If you have one Good and Successful Project (Chengdu J-20), It's better to Focus your money and resource to that project.
And like we see, (Chengdu J-20 Project) is in a Good shape and very successful until this day.
BTW, If you compare J-20 and FC-31.
J-20 is Superior in every aspect (from Payload, Fuel Capacity, Maneuverability, Combat range, Avionics, and many others)
But, like other members said,
Wait and see
We cannot have Conclusion based on Rumors.
About China's Future Aircraft Carrier.
In the next years (Type 002, Type 003 Aircraft Carrier)
Will get Bigger Tonnage ( at least 75,000-80,000 Tonnes) and also Catapult (Steam or EMALS).
So, if PLAN choose
J-20H Naval Variant. It's indeed a very Good choice.
Chengdu J-20 size is almost same like F-14 Tomcat in America.
And with Catapult Launching Mechanism, it's not a problem to launch Chengdu J-20 from their Future Aircraft Carrier.