Technically, when you say iPhone, you are refferrring to the 2g which is not longer sold in stores. If you were asking about the 4 and 4S, then here are some new features the 4 does not have. twice...
Unfortunately, the iPhone 4 is designed to operate on the downloaded version. It can not be programed as an iPhone 4S. However, check with your carrier to check when you are able to upgrade. At that...