For business visibility, going with just the AMD brand still makes more sense. Easier artwork, etc etc.
People will always BUY Radeon graphics cards, but seeing the ATI logo on the box is helpful for the sub-conciseness buying market. Did MS create a whole new brand for its XBOX? No confusion there. Or how about SONY and its gaming products?
For AMD to grow the brand, they went the right part. The only thing is, ATI has the cooler sound and logo.