My Photoshop CS6 Beta had expired as well. I followed the purchase link, signed up for the discounted $29.99 a month plan and followed the instructions in the confirmation email I received within a few minutes. I ended up downloading a new version of the Adobe Application Manager and then downloading a new (non Beta) copy of Photoshop CS6. This version gave me the option to sign in with my Adobe ID which immediately activated my copy. No serial number required. I think Adobe could make this process more clear than they have, but I can't fault them for delaying my activation.
