I don't think dev time would be well spent attempting to add a new race to a game such as this, without severely undermining the point of the games uniqueness. Possible? Sure. But at what cost? What might now get developed because resources are allocated elsewhere? That said, it's possible they could mimic "hero" classes that start at a certain point in the game (like, a class that starts IN the new xpac, skipping all vanilla story line and leveling). There are ways to minimize, but I don't think the community would appreciate many methods necessary to pull it off.