why are you guys giving weird information and making weirder assumptions here?!!
How many total BTC are held by Huobi, OKCoin, and BTCC?
A lot. According to Bloomberg[1][2] the yuan accounted for 98 percent of bitcoin trading in the past six months so If that ever happens , It definitely won't be beautiful.
the answer to OP's question is unknown and there is no way we can possible know that for sure.
what you are showing here is
trading volume not how much they are holding. for example if you sell 10
BTC at 5050 CNY and buy it back at 5000 CNY (zero fees both ways) the volume exchange reports will be 20
BTC and so on. but exchange after this has 0 bitcoins and do this 50 times * number of traders doing this. and i am not factoring in the fake volume they report. (and remember there is 16M coins in total and they are reporting 200M)
you can however check
https://www.walletexplorer.com/ for the wallets associated with these services and interestingly enough
huobi has 1415
BTCOKCoin has less than 100
BTCbitstamp has 4100
(although you have to do more analysis to find out the real balances the above are just a quick look)
~ Probably the biggest instadump ever.~
how?
lets assume government seizes the bitcoins on these exchanges and they have 98% or whatever crazy percent people think these days. then who has any bitcoin left to dump? lol