That is a question that is utterly and completely impossible to answer. The fact is that no one can predict what World War 3 is even going to be like. It could be next year, it could be two hundred years from now. Because we don't know when it's going to happen we don't know what kind of technology is going to be used or what kind of environment is going to decide it.
Therefore , if we don't even know what to or is going to be like, there is no way to predict how currencies and commodities are going to work. Changing rapid technologies makes it really difficult to predict.