Meet the RQ-170 Sentinel. The Air Force has confirmed the existence of the "Beast of Kandahar". It has been seen flying in Afghanistan since 2007 and is a product of the infamous Lockheed Martin "Skunk Works".
More info at Aviation Week.
Remember, the Predator started out as an unmanned recon aircraft. It didn't take long to strap on weapons and take advantage of the platform's capabilities. Given the RQ-170's power, performance and stealth, is a fighter/attack version far away? Or is it already in the air?