Credit for this find goes out to Tom over at the iPhoneBugList, who stumbled upon the reference while attempting to interface his own site with Apple's iPhone feedback form (which is where the reference was spotted).
Nestled within the HTML code for the feedback form is a hidden variable called "product" which contain the value "iPhone Extreme." Unfortunately, that's the extent of the rumor.
Obviously, speculation is that "iPhone Extreme" could represent some new product down the line, a new name for the current iPhone if a cheaper and less capable version is released, or simply nothing at all.
On the other hand, this hidden variable with its associated value of "iPhone Extreme" is currently being submitted to Apple's feedback script each and every time a user fills out the form.
So either Apple is not yet checking for the variable upon submission, or the company is well aware of the naming convention and has implemented it in such a way for a specific reason. It will be interesting to see if the code changes in the coming hours.
Update: The "iPhone Extreme" reference was simply a sloppy copy-and-paste job on the part of an Apple webmaster who apparently used the company's existing AirPort Extreme feedback form in creating one for the iPhone.