This process is highly politicized. Read Food Politics by Marion Nestle to get an insider's view of what goes on. For example, in the existing Food Guide Pyramid, finalized in 1992, the beef industry played an aggressive role in making sure the guide never recommended that people eat "less read meat." Instead, the guide was modified to read something more along the lines of, "Increase consumption of lean meats," which is very different from the intended, scientifically supported health advice of "eat less red meat."
The new Food Guide Pyramid will likely be even more of a handout to food producers. Farmers and food manufacturers have been put through the wringer over the Atkins Diet and low-carb diets in general, so they know how powerful nutritional guidelines can be if the public pays attention. Watch for every prominent food-related industry to play politics in an effort to get favorable placement in the new guide: the dairy industry, the sugar industry, meat producers, grain growers, produce farmers... you name it.
The USDA, of course, consistently caters to industry rather than actually looking out for the health interests of the general public, so you can rightly expect whatever new guidelines the agency produces to be little more than heavily politicized propaganda designed to appease powerful food lobbies. It's a given, even before the process has begun.
Want real nutritional advice? Read the Atkins Food Guide Pyramid, which offers far better nutritional advice than anything the federal government has come up with. After all, to get the real story on nutrition, you have to listen to people who don't have financial or political ties to food producers, and the USDA is so intertwined with food producers that it can't possibly remain objective or scientific about nutritional guidelines.