I found this over on macintouch.com.... Interesting.... I figured I'd cross pollinate it over here.
Macintouch contributor said:I was at my local AT&T store this evening eyeing the iPhone. I asked the representative if they had any 4GB models still in stock. She said no, they only had the 8GB and 12GB models in stock. I was shocked to hear 12 GB, and she immediately noted my shock and tried to back step her comments....it seemed like she knew something was coming and had let the cat out of the bag accidentally. Obviously this is just a rumor, but it sure seemed like she knew her stuff in regards to the iPhone so maybe there is a 12GB model on the horizon.