I remember wheat prices surging to over 1200 a bushel a couple of years ago, during that time prices of everything containing wheat of course surged, fast forward to today, wheat is down over 50% from it's highs but prices of bread, bagels and pizza, etc still remain the same.
I have noticed many commodities getting there turn at these huge big increases like cotton, wheat over the last 2 years only to drop significantly later on.
As for sugar, who knows how low it goes, they are trying to pass a soda tax and pepsi just announced it's pulling it's line of sodas from schools, how much impact this has on the price of sugar I really don't know but I'm sure people are reading between the lines.