Not sure what is happening federally. California has a law that started a phase in this year. Each year over the next few years, a larger % of the total toilets that a manufacturer sells in CA has to be 1.28. Finally, in about 2012 or so, ALL have to be 1.28.
Some manufacturers are putting out a toilet that is just straight up 1.28 gpf. Others opt for the "average" method. It is assumed that there is some kind of ration of #2 flushes to # 1s, so you can flush 1.6 gallon with one button, 0.6 with another. It averages to 1.28 gpf or less.