Recall Timur Kuran's theory of preference falsification: many people follow the herd rather than revealing their true views, and this is most common in autocracies. In those cases, public opinion may suddenly flip. WikiLeaks, by making some truths common knowledge, has its biggest effects on autocracies, even if the leaks are from the United States.
Two possible results of the recent revelations could be that the Sunni Arab autocracies will have to cozy up more to Iran (their citizenries don't hate Iran so much, and so they might filp against their own leaders) or that China abandons North Korea altogether. In the former the government has to match the public opinion and in the latter case perhaps the public opinion can flip against North Korea and confirm a trend already underway in the government.
What about democracies? The most likely result (though not from this recent batch) is to encourage war-mongering attitudes against potential enemies, due to perceived slights. Such feelings are usually produced collectively, and subject to sharp triggers, following the revelation of knowledge or pseudo-knowledge. Remember the Zimmermann telegram?
Here are comments from Douthat and Wilkinson.