What a joke.
1) wants to leak them (most of the Chinese people who I've met in China, especially those who work in a government or military capacity, will bend over backwards to defend China from any level of perceived foreign criticism)
2) has the capability to leak them (most Chinese people are unlikely to know much about Wikileaks)
Wikileaks legitimately may not be in a position to acquire such documents to leak. My understanding is that they mainly distribute documents provided to them by others, and has never exercised much editorial discretion. If Wikileaks is best known in the US/Western Europe, it'll likely only acquire documents related to those regions.
For a Chinese person to leak documents about Xinjiang to Wikileaks, that person must first know about them, then be able to contact them, then be able to send the documents to them. I wouldn't be surprised if Wikileaks itself is blocked by the Great Firewall, and that its typical communication channels for leakers are blocked and/or difficult to use from the PRC, which makes the whole process doubtful.