It should happen right away I believe. As soon as the next block after the 2016th is accepted, the difficulty updates. The transaction rate would only be affe

It should happen right away I believe. As soon as the next block after the 2016th is accepted, the difficulty updates. The transaction rate would only be affected for a max of two weeks as I understand it. As for how the 'market' would react if all Chinese miners dropped out, I have no idea :)