I was just told this exact same thing when i called. She just said all i needed to have was an active att account,which i obviously do. This was from someone in the business coustomer support dept.
The sad fact is that no one knows for sure until the official announcement, and that probably includes the AT&T executives who have been quoted. They are still figuring out exactly how this will all work. I'm hoping existing customers who are not upgrade eligible won't get screwed too badly, it would be nice for them to decide that 199/299 is really for everyone regardless. However, I'm a realist so we'll just have to wait and see. Anything a customer service rep tells you at this point is pure speculation, no matter how sure they sound. I went to an AT&T store to ask some questions and the guy was basically clueless.