According to fiercewireless ..
At the WWDC conference yesterday, Apple CEO Steve Jobs told developers
that they didn’t need an SDK to write apps for the iPhone–they can
start building Safari-based mobile Web 2.0 apps now. In other words,
don’t expect to be able to develop native iPhone apps any time soon.
Looks like Ajit Jaokar was probably right when he predicted
the iPhone would be a major catalyst for mobile AJAX back in January.