Thanks for the responsehttp://www.worldofwarcraft.com/cataclysm/faq/
Here is what they said. If you cant click on link.
Is another Hero class being added to the game?
We are not planning to add a new Hero class in World of Warcraft: Cataclysm. For this expansion, it was more appropriate to focus on the two new races, the goblins and worgen. We never intended to include a Hero class in every expansion. As you saw with death knights, adding a new class changes the dynamics of the game dramatically, which is not something we want to do in every expansion. We still have plans to introduce new Hero classes in the future