How can you say that with any confidence whatsoever when is a real possibility that China could in the coming decades have an economy that is more than 3x or even possibly 4x the size of the combined potential opponents in the region (USA included). This isn't even an outside shot, it is the most likely outcome.They won't ever have the same number of 5th gen fighters as the combined potential opponents in the region
If you hold that to be true, then you must think that China's aviation industry will always lag significantly behind its development. Even if China's overall size of industry, GDP, national net worth, etc. is only 2x the entire region (not an unlikely feat, with current projections of this happening in about 15-20 years), then how can you not think that China's aviation assets (both military and civilian) will never reach a commensurate status?
You must either be
a) Very pessimistic on Chinese growth outlooks, believing that China will never so much as reach 50-60% of US living standards (as assessed by proxy metrics like GDP per capita and median household net worth), and therefore simply never have the size to even attempt to produce the quantity of such aircraft
b) Believe that China will never have an aviation industry that can produce the quantity or quality of output that the US can (+20% for the combined non-US forces in region), regardless of how many multiples China's economic size, or industrial size, or manufacturing size is over the US.
The latter (b) is even more pessimistic because it implies that even when Chinese living standards finally approach developed levels and fully catch up with Western levels, that China will still always be qualitatively inferior.