Preview at WWDC likely in June, followed by September launch.
Steve Jobs Offers Explanation About iPhone SDK Changes Restricting Adobe and Other Cross Compilers
Jobs reportedly points to John Gruber's analysis of why Apple might have implemented this. Gruber argues that Apple wants control over native iPhone OS development and cross platform solutions would dilute iPhone-exclusive and iPhone native apps.
If that were to happen, there's no lock-in advantage. If, say, a mobile Flash software platform -- which encompassed multiple lower-level platforms, running on iPhone, Android, Windows Phone 7, and BlackBerry -- were established, that app market would not give people a reason to prefer the iPhone.
And, obviously, such a meta-platform would be out of Apple's control. Consider a world where some other company's cross-platform toolkit proved wildly popular. Then Apple releases major new features to iPhone OS, and that other company's toolkit is slow to adopt them. At that point, it's the other company that controls when third-party apps can make use of these features.
We've been there before, and intermediate layers between the platform and the developer ultimately produces sub-standard apps and hinders the progress of the platform.