People keep looking at raw numbers about how much fighters America has against China, but fail to realise that they would never send all their fighters in a potential war scenario over Taiwan. Leaving a portion to defend your home nation, portion near Europe and Middle East, would effectively cut out a chunk of your so called 2000 F35.No way they will think just 600 will be enough if US plans to have 2000 F-35. China also needs to take into account the Air forces of Japan, Sk, Taiwan and Australia. China needs to have at least equal number of planes than US and its allies. Ideally it should overmatch it if it intends to force US out of West Pacific without a fight. Only massive numbers and quality can do that.
I think China will eventually have around 1500-2000 J-20 in the future. But I don't think all of them will be Air Superiority variant of the J-20. They will eventually move towards a Fighter-Bomber/Multirole version of the J-20 with more focus on ground strikes. Maybe the twin seater J-20 will focus on that in the future.
I expect these twin seater J-20 to eventually replace the Ground strike focused flankers in the PLA.
So after 1000 J-20 the rest of J-20 will focus on ground strike while Air superiority mission will be given to the 6th Gen fighter China comes up with.
Meanwhile China can deploy majority of there fighters in Taiwan scenario as its basically home turf along with anti air coverage.
If we look at inventory America deployment of their assets based on % is far less than what China can offer.