Mardi Gras at WDW is busy when it coincides with President's Week or Daytona week, otherwise it is a great time to go.
SInce it is Feb. 8th next year, as WANNABE points out, it does NOT coincide with either event, meaning low to average crowds.
There will be TONS of New Orleanians there, however, escaping the living hell known as Mardi Gras.
Hope to see you at WDW.
DD does have a Mardi Gras celebration (which we also avoid)