Actually John, this story quotes energy production (in TWh) not capacity additions. So it already accounts for differing capacity factors of wind and coal.
"Thermal power use, which is predominantly coal, grew by only about 0.3 percent in China during 2012, an addition of roughly 12 terawatt hours (TWh) more electricity. In contrast, wind power production expanded by about 26 TWh."
However, it's somewhat mislead for another reason: the reason coal output grew so little this year is because coal output was very high in China in 2011. That's because 2011 was a low precipitation year in China, and hydropower output (which supplies a big slug of China's power) was very low, with coal plants making up the shortfall. Rainfall and hydro generation rebounded substantially in 2012, up 196 TWh year-on-year, versus about 26 TWh for wind.
So yes, growth in actual wind generation exceeded coal-fired generation this year. But that's less a sign of wind's rise than the yearly fluctuations of hydro and coal output driven by precipitation patterns.
Wind is growing fast in China, but has not yet eclipsed coal. And as you say, hopefully these trends do not lose momentum in the near future.
For more on China, see this "2012 energy report card" from Trevor Houser at Rhodium Group. A hat tip to Trevor and Robert Wilson for explaining these trends to me on Twitter yesterday.