I would think that, in China, money is steadily leaving the system: Chinese traders seem to be gradually selling and taking their cash out of the exchanges. This feeling is not based on the exchange volumes, but simply becuse of the decay of the China bubble (which seems to be too fast to be due to miner dumping alone). The rest of the world should still be a net buyer, but there is no data, really, and apparently it can barely absorb what the Chinese and the miners are selling.
There is no "money" entering nor leaving the bitcoin system. Bitcoin is money, so is USD, CNY etc. What happens is that
value moves from one money system to another. When the revaluation of money system is not the same in all actors' minds, there has to be trades. If all actors at the same time and to the same degree change their valuations, there need not be many trades.
Indeed you are right, there is no USD or CNY in the "bitcoin system", so there is no sense saying that money is going into or out of it. I should have said instead that, in my opinion, more and more Chinese traders must be selling their holdings for whatever others want to pay, and dropping out.