Off of good ol' wikipedia

In July 2003, current Atlanta mayor Shirley Franklin announced a second international concourse, which will also have its own terminal. The new terminal will be called the Maynard Holbrook Jackson, Jr. International Terminal. It was slated to open in 2006, however time and cost overruns led general manager Ben DeCosta to cancel the design contract in August 2005. The very next day the company sued the airport claiming "fraud" and "bad faith", blaming the airport authority for the problems. This will likely push back the terminal's completion to 2010. [2]

Also scheduled to be completed for 2010 (though it too may be pushed back now) is a South Gate Complex, a new terminal south of the current terminals. The new terminal is expected to include approximately 31 gates.