the iphone 4 is the fourth generation iphone.
it will not have "4th Generation" network capability.

For instance this is a ipod nano 4G. It did not contain a 4G cellular modem (or else I wouldn't have been so quick to sell it)

no 4G source (+ common sense): http://www.product-reviews.net/2010/...why-no-4g-lte/

As far as AT&T's shrinking overage. I have AT&T (and one of their dumbphone "messenging" phones; supports 3G w/ HDSPA). And let me put it this way, I used to be able to make phone calls on it at home (with 4/5 "bars" of 3G). Then suddenly not able to (0 bars). Same goes for other places I frequent.