Last year everyone got a sneak pic (although crappy resolution) of the iPhone 3g because Apple included an icon in their SDK at the time for the new model. The icon is the one used in iTunes (it shows the image of your phone).
The icon for the the iPhone model due to be announced and released in the upcoming months has been found in latest SDK for iPhone 3.0 beta 5 firmware. The icon references iPhone version 2,1 which is the next iPhone. The original is 1,1 and the 3g is 1,2.
Sadly this time around it appears that Apple isn't making the same mistake. The icons for iPhone 2,1