If China were to shut down bitcoing mining, my understanding is that the worst case scenario is much more dire. The network only adjusts the 'difficulty' relative to current network hash power every 2,016 blocks. Depending on the severity of the overall hash power reduction, new block discovery might slow down significantly. This would also delay a recalculation of the new difficulty accommodating the reduction in hash power.
The network could be severely throttled for weeks.