There's been some confusion in the branding of various cell phone services over the years. The way that the various companies change hands, get bought out, merge, and so on, has meant that there have been all too many changes in name. To the point that people might not actually realise that the service provider is in fact one of the great names of the business, or is just another start up.
One example of this is the way in which the cell phone division of AT&T was, a number of years ago, branded Cingular, to give it a different public profile from the rather old fashioned, even stodgy, implications of the AT&T brand. This worked at the time, as the parent company was still seen negatively, from hte time when it had a virtual monopoly on long distance calls.
All of that has rather changed now, and so the Cingular / AT&T branding issues have also. The parent company is seen as being one of the few reliable providers of solid telecoms services, in direct contrast to the way in which many of the cell phone companies are seen as somehow disreputable. So changing the name back to AT&T makes sense, in that some of that glow of solidity will rub off upon the cell phone subsidiary.
It's likley that the newly named company will be launching it's own phones in the near future and it's highly likely that the first one will be the new Apple iPhone. Many people think of this as a Cingular exclusive and it's certainly likely that they will be providing the best deals on it.