Tidbits has a scoop that those who are in a Family Plan, and are not eligible for an upgrade for iPhone 4, can transfer eligibility to or from another family member. This could be quite useful for those who may not want to incur the $200 premium for upgrading early.
There are a few catches, though. First, this cannot be done online. You are being recommended to call AT&T to place an order to avoid any confusion or excessive fees regarding the price of the Phone.
As stated in the Tidbits article, you could work around this before by swapping SIM cards, but with the transition to the micro-sim, this cannot be accomplished so easily. That said, it is possible.
You can check your eligibility by calling *NEW# (*639#). A free text-message will be sent to you with your eligibility date. This is what it looks like on an iPhone.
Most everybody who purchased an iPhone 3GS last year, or had an eligibility date in 2010 should be able to upgrade to an iPhone 4 for the same rate as those who had contracts expiring in June or prior.
Eligibility for upgrades depends on several factors. The cost of your phone plan, how long you’ve been an AT&T customer, and when you purchased your last iPhone. For instance, my girlfriend transferred her phone in March of 2009 and won’t be eligible for an upgrade until January of 2011. However, I bought my iPhone 3GS on launch day last year, and I’m eligible for an upgrade on June 25th.
Article Source: Tidbits.