Preview at WWDC likely in June, followed by September launch.
Apple COO Discusses iPhone Exclusivity, SDK, and Unlocking
Of interest, Cook answers why Apple hasn't offered an unlocked version of the iPhone. He states that multi-carrier offerings were impractical at launch. For the U.S. market, this would require a CDMA and GSM version of the iPhone. In the end, they felt it was impractical to try to satisfy every carrier and every user. Still, he states that Apple is "not married to any business model" and instead, they're "married to ... shipping the best phones in the world."
When asked about the possibility of Apple expanding into even more areas with new product lines, Cook feels anything is possible, but that each product choice is made carefully since "for everything we do, we know me make a choice not to do something else. We may or may not add some over time, we'll see."
Regarding iPod reaching a saturation point, Cook points out that 40% of iPods are still being sold to those who don't already own an iPod and suggests that slower iPod sales are a reflection of the economy than necessarily sales saturation.
He again describes the iPod Touch as the "first mainstream WiFi portable platform" and also describes the iPhone as a "platform not a product", and states that the upcoming SDK will "broaden the platform more, to the point where the only limit will be peoples imagination." Cook stopped short when asked about when the first 3rd party apps would appear, not wanting to take away any element of surprise from next week's event.
Finally on iPhone Unlocking, Cook acknowledges the problem but states he "look[s] at this 'problem' with a little bit of a smile. Having people stepping over each other for the phone isnt a bad thing. He goes on to state that the best way for Apple to fight back is to offer the iPhone in more countries.
A Quicktime stream of the talk is available from Apple.