If government agency, private enterprise, Dr. Evil, etc had new technology with more hashing power than the entire Bitcoin network they could find a better use for it than forking or double spending attacks on Bitcoin. A government agency possessing new technology with that much power would want to keep it secret. If anyone else openly advertised the fact they had such technology by attacking Bitcoin they would find themselves rapidly targeted by a number of government agencies attempting to get it off them. The NSA/CIA would love to get their hands on new technology with that much power.