So the new handset from Apple is called the iPhone 4 and not the 4G as all the pre-announcement hype would have us believe. This might be because the handset is not actually a 4G capable device and there might not be one until 2012.
Dvice.com is running a story debating what is the hold up with an Apple 4G device, and when one might be available. At the moment Sprint are the only carrier who has a 4G network, and Apple currently have an exclusive deal with AT&T which is expected to last until 2012.
AT&T is a long way off having a 4G network and is currently lagging behind both Sprint and Verizon in the 4G stakes. Until AT&T or Verizon have a large enough 4G footprint it is doubtful Apple would launch a 4G device for the mass market.
Apple will probably wait for the LTE technology to be available that AT&T and Verizon will use as it will be the most available worldwide. For all the possible reasons for the delay see the article here.