Yep, because it gives everybody something to do after they cap the maximum level on the last expansion. It is a way to lure in more buyers and give the veterans somethings to do.
They released the cinematic trailer today.. beautiful stuff. Yeah.. still making expansions.. the game would die if they didn't. I'm already bored of the Cataclysm one and that's saying a lot because I'm addicted to the game.