You are correct that the long term capital gain rate is currently 15%.
As the law stands the long term capital gain rate in 2011 will revert to the 2001 rules of 20%.
See http://www.taxfoundation.org/publications/show/2088.html for charts.
Of course, no one can be sure what may or may not happen between now and the end of the year in Congress.
So, as the law stands, it is 15% in 2010 and 20% in 2011 for long term capital gain.