Now, you may read this and go "oh, not another rumour", but this is some real, replicatatble evidence found in the iPhone SDK (3.0, beta 5).
Whenever you launch iTunes, it has a pic of your iPhone's model. This is the same as with the SDK (in Organiser). While searching for an un-related file in Spotlight, it turned up an image deep into folders called "iPhone 2,1". A quick tweet-out told me that the current iPhone's model number is 1,2, so I thought I would put my findings here.
Firstly, the folder's contents:
If you have the 3.0 beta 5 SDK installed, head to:

(info from the "Get Info" window)
Why I think the image is 100% real:
- The SDK has been known to reveal details about up-coming models, including the leaking of the magnometer in the 3.0 SDK, and the details abut the 3G chip in the 2.0 SDK
- As Apple Stated, they use exacty the same apps in-house to develop their apps and test them on their products
- There is obviously a new iPhone coming soon, so it was just a matter of time before this was found
The images of iPhone 2,1 can be found
here (black) and
here (white)