The company claims the AMD brand is stronger than ATI, and that now is the time to make this move, because Radeon graphics cards are experiencing good sales, and the firm currently has a high market penetration in the GPU market.
AMD explains its move as an "evolution of the AMD brand portfolio", saying that consolidation of ATI-branded products under the main brand results in reduced marketing overhead. It claims to have surveyed several thousand discrete graphics-aware users in in the U.S., U.K., Germany, China, Japan, Brazil, and Russia. The survey revealed that when made aware of ATI-AMD merger, AMD preference triples; AMD brand is stronger than ATI (against graphics competitors); and that people see Radeon and FirePro product names more conspicuous than ATI, indicating a "permission" to consolidate ATI into AMD. The survey was conducted entirely by AMD.
The company also claimed that this is the perfect time AMD could possibly consolidate ATI brand, because Radeon products are experiencing good sales, and there's high market penetration of AMD's graphics products. Finally, AMD revealed the new brand logos that are nearly identical to the present ATI logos, of course, minus the revered "ATI".
Source: TPU