You'll know when the Bank stop processing withdrawals. The price of Bitcoin will shoot up. So long as you can get fiat out the FUD drivers people sell Bitcoin's, and withdraw fiat, when you have fiat on an exchange but can't withdraw it you buy Bitcoin and withdraw that.
The effect shoots the price up. It's FUD untill we see people panic buy into Bitcoin.
True ... if CNY withdrawals are suspended without advance warning, and the client's yuans get trapped in the exchange account.
But if the clients will have some advance warning, as the Caixin rumor claimed, I supose that most of them would sell (maybe even panic sell) their coins to arbitrage traders or hoarders, and take the cash out before the deadline.
Moreover, if CNY withdrawals are suspended, arbitrage between the Chinese exchanges and the rest of the world may become impossible. In that case, even if the price shoots up at the Chinese exchanges, it will drop somewhat on Western exchanges, as they receive the Chinese coins but not the Chinese money.
I can't see how a decline of bitcoin trading in China could lead to a price increase. If the blocking of bank accounts turns out to be a false rumor, as Huobi's note suggests, then perhaps the price will recover in time to the 3000--3500 CNY range (500--570 USD), even if the 3rd party channels remain closed. If the bank accounts are closed too, the price in Western exchanges can only go down.