Does China's de-pegging the yuan have anything at all to do with this?
They didn't really depeg, just repegged to a currency basket. But the formula is secret and they moved a whopping 2%. Big Deal.
But to answer specifically, in the short run a depeg will lower the dollar and raise oil prices per dollar. But in the medium to long run, depegging will slow China's growth and energy use (or crash it altogether) and we would see a large drop in oil prices. Supply and demand are tightly balanced right now and it won't take much of a demand decrease to drop the price.