Read your own link and compare it - it sounds different to me - more conservative. "Chang indicated that 28nm processes will likely contribute 10% of 2012 revenues." besides the relative % of 28 nm is somewhat meaningless because it's based on absolute sales.
That was seven weeks ago: Taiwan Semiconductor Manufacturing Company said this week that the ramp up of chip production using 28nm process technology will be fast and the technology will contribute to 10% of TSMCs wafer revenue already in the second half of 2012. Although sales in the Q4 2011 were lower than expected, the world's largest contract maker of semiconductors believes that chips made using advanced nodes will continue to be in demand. 28nm to Ramp Up Rapidly