We may be in for a treat at the Apple iPhone announcement on October 4th. China Unicom vice president Huan Wenliang announced at MacWorld Asia that both T-Mobile and AT&T would offer the iPhone 5 with HSPA+ 4G capability.
This means that the iPhone 5 will support speeds up to 21Mbps over HSPA+ which is much faster than 3G as long as the network is not congested. Apple has stated before that a move to 4G would be premature as 4G networks to not have enough coverage yet in the United States to add a bulky 4G antenna in the iPhone. However if Huan Wenliang is telling the truth then I would expect 4G coverage on the iPhone 5 in markets that support it.