Update: New information has risen on the matter, according to which AMD has no plans of dropping the ATI brand name at all. This is part of the response Ars Technica reportedly received from AMD Public Relations team:

"AMD has no plans to drop the ATi brand name or ATi's product brands. The ATi name will live on at AMD as our leading consumer brand, and so will the Radeon brand and other ATi product brands. AMD's executive management knows very well the power and value of branding, and ATi's branding is some of the most valued in the global technology industry."
Despite of the contradicting information, we would give credit to Ars as being the most reliable source at this moment.

Previous coverage: According to reports around the net, AMD could be dropping the ATI brand name altogether after the acquisition process has been completed. No official statements have been made on the matter yet, and perhaps for the general audience it won't be a big deal to start seeing AMD Radeons sometime soon, but for us enthusiasts, it does have a bit more impact than that.

We asked Richard Baker from AMD if this meant that the memorable Radeon name would also be biting the dust, but he replied that 'we haven't made any final decisions yet, but I'd personally be very surprised if we dropped any of those product names. The ATi company name is definitely going, though.'
AMD always made clear that the new company would operate under its brand name, but if this article is to be believed the acquisition should then be treated more as a takeover than a merger.