First of all, what you say did not make sense.
If you ordered 200 J-20 for use and only to find if they are capable, then China will mass produce J-20 in thousands.
The problem is, when you order the initial J-20 Production (in 200 as you said) will you order other J-series aircraft? If you do, then what happened to all those J-series aircraft (J-10/15/16/31) when you order 1000 more J-20, which is in thousands? You are going to scrap them? Or you want to sell them? If you do not order other J-series aircraft and wait to see if J-20 is capable, then are PLAAF.
It would be super fail either way as if you did order other J-series aircraft, you waste billions of dollar for producing other J-series to back order J-20, or if you don't order other J-series aircraft. Then you only have 200 J-20 to defend the Chinese skies until you can make 1,000 of them, as you say, and you cannot make 1000 J-20 appear out of no where, you need at least 10 years to make them, giving if the Chinese Aircraft industry is as mature as the US, which turn out 30 aircraft at per years.
And you actually have no idea why the US cancel the order of F-22.
US Stop making F-22 simply because the edge is over the next competitor, the Russian.
When US start making F-22 in 1990s, Russian did not have a single aircraft that can fight F-22 1 on 1.term. And the edge is secure with the F-22 even though there are only 180 F-22, simply because US does not only have 180 F-022, they have 300 F-15E, 1600 F-16, 500 F-18 as well. US DOD Calculated that it will be at least 2030 before any country can amass a stealth fighter force that can answer to the F-22 in a 1 on 1 scale.
Depending on manufacturer capability
China claim J-20 will enter IOC in 2017, that mean in 10 year, in 2027, China would have about 200-300 J-20 in service.
Russia Claim PAK-FA will enter IOC in 2020 which mean by 2030, Russia would have 200-300 PAK-FA in service
By 2030, however, US would have already move on to 6th Generation Jet Fighter (Due at 2025) and about 600-700 F-35 in service, it would be wise to invest on the next gen as any F-22 make now is actually counter productive to cost. US could have 500 F-22 now, but what for? They don't need that much F-22 to go against Su-35 or J-15 which in low hundreds. Making that much is simply waste of money. US stopped production of F-22, does not mean they cannot make it anymore or the production line is dissembled, they can pump out F-22 as we speed, if they were in need of those, 24 F-22 is waiting for 1 year of time and about 2 billions of dollars away.
You have 600 billions US Dollar budget, that does not mean you have to waste them, it's far better to get involve with 6th Gen program than to keep making F-22. That is the reason why F-22 is not making at this moment.
However, if China claim and showed proof that they actually have 500 J-20 now, US will reopen the F-22 production line. Otherwise it would be both a waste of time and money.