The famous argument of AMD spec fanboys is that AMD will allways go on with providing full specs for their hardware while binary blob support can eventually break. In fact the truth is the opposite of it. It appears that the false opensource prophecy can break any time soon:
From that text:
Will opensource "drivers" from AMD support OpenGL 3x/4x and video acceleration in the future? Given the patented floating point support in OGL 3 and s3tc and these DRM arrangements, I've my doubts.The only way to protect the HFS process therefore is to not release any technical details on the device beyond a minimum required for web site reviews and comparison with other products.
So amd linux users will have half-baked featureless opensource drivers when amd will drop binary driver support for r600/r700 hardware and another waiting period will start for these people to be able to play OilRush.