I have spoken to those who work in Christian missions in China and they feel the Christian administrators deliberately downplay the christian presence as not to upset the Chinese authorities. When Chinese authorities say there are X number of Christians in China the Christian groups accede knowing it is not true and in return the authorities allow much greater leeway for the dissemination of the Christian message.
These Chinese Christian leaders know the Chinese monitor presence of Islam throughout the world and are concerned with its violence.
Expect to see a silent surge in Christian presence in China but one that is not publicized.