AT&T may discount the new Apple 3G iPhone up to $200, according to Fortune. In addition, the new handset is expected to come in 8 GB and 16 GB versions priced at $399 and $499 respectively. The new model is also expected to be thinner than its predecessor and include a GPS navigation chip.

The Fortune article predicts the new Apple 3G iPhone Release Date as June 27, on the 1-yr anniversary of the original iPhone’s original release. Previously, we had reported on predictions that the iPhone would be released on June 9, when Steve Jobs is likely to deliver his keynote speech at the Apple WorldWide Developers Conference In San Francisco.

The new AT&T discounts will only be available through AT&T, and will not be offered to customers who purchase an iPhone from an Apple store or Apple.com. This discount is so steep it seems clear Apple will need to offer some sort of competing offer of its own in order to sell any handsets itself (I’m thinking a $200 Apple store credit).

How will AT&T cover this discount? It shouldn’t be difficult, as the average iPhone user carries a monthly plan which is around $100, or twice as expensive as the average cellphone plan. Handset discounts are traditionally a favored marketing tool because of this ROI relationship.

If the discount rumor is true, it is clear that both AT&T and Apple are focused on upgrading existing iPhone users and extending their contract another year. Apple has proven itself as very adept at stepping new iPods up each year to a level which encourages people to upgrade, and they are clearly doing the same with the iPhone.

So the question now is “what will they do next year?”. The AT&T exclusivity agreement with Apple expires next year – so Apple will be open to sell iPhones through other carriers like Sprint, T-Mobile and Verizon, which will probably result in the largest saturation boost for the device since its launch.

Another likelihood is that I predict the first Apple 3G iPhone will not allow tethering, or surfing 3G over your laptop via the handset over USB or Bluetooth. This could also be a holdback for next year.

It will be interesting to see what happens to the handset market if both Sprint and Verizon do carry the iPhone next year. As the iPhone expands its reach, the Blackberry is also gaining ground in the consumer market and prices for both devices will be going down. A discounted $199 iPhone is not only scary for other smartphone lines, but also presents a looming problem in the lower-price tier market of handsets as well.

Until now, handsets like the RAZR have been enjoying success on Verizon and Sprint without iPhone competition and on AT&T via price differential. On all carriers, users who insist on 3G (like me) have also buffered the iPhone effect for handsets which have 3G, especially in the Blackberry line.