In a press release, Valve said that "CS: GO features new maps, characters, and weapons and delivers updated versions of the classic CS content (de_dust, etc.). In addition, CS: GO will introduce new gameplay modes, matchmaking, leader boards, and more."
Valve has also been kind enough to go ahead and put a listing on Steam, so might as well add it to your wish list.
Just when you think you have that Counter Strike habit kicked...
(I can't wait!)