I refuse to believe that this would ever exist.
up until about 6 months ago i still had a hard wired router, i never used my HTC on Wifi, if the router hadnt finally died i would still be using it today and would not be connecting my iphone through wifi.
i can see a market for a low end non-wifi phone
I'm more doubtful in the fact that "there will be a low-end iPhone."
Not to mention that a lot of apps and features, such as iTunes store (for over 12MB purchases) and the App store and such would be essentially useless without wifi because they don't allow you to download anything above.