Usually bureaucrats think the law is sacrosanct, it's what we do. But the dirty reality is laws aren't self-executing; there's lots of provisions enacted into law which become a dead letter. The price of milk in 2013 should be one of them.
Without a new farm bill, the provisions of old law come into effect. That means for milk the government is supposed to support the price at a level which means $8 a gallon. But suppose USDA doesn't do so? Theoretically some group, presumably milk co-ops, could haul out their lawyers and file suit in federal court to force USDA's hand. My theory is, by the time the suit is written and filed, and DOJ works with OGC to come up with a reply, new law will have superseded the old law, and Congressional attorneys will have put in a provision which essentially nullifies the suit. Net effect: consumers don't see a rise in milk prices.
[Update: This is an example of why there are dead letter provisions: if the bureaucracy doesn't act on its own to implement a provision of law, there needs to be someone who can take USDA to court and/or with enough PR clout to raise a stink about it. In many cases there's neither.]