Navigate to the Settings pane in the iPhone emulator included with the iPhone SDK released yesterday and you'll notice something interesting: the OS version listed is 1.2 (5A147p). This unreleased iPhone OS revision is code-named "Aspen," and includes many of the new frameworks and other components that can be accessed with the SDK but are not included in the current public iPhone OS release, 1.1.4.
The "Aspen" moniker falls in line with previous, ski-resort-related code names for iPhone OS releases. iPhone 1.1.1 was called SnowBird; 1.1.2 was Oktoberfest; 1.1.3 was LittleBear, etc.
It remains to be seen whether iPhone OS 1.2 will be released to the general public or constrained to the emulator. iPhone developers will need a way to test their applications on actual iPhone hardware utilizing the new frameworks and system components -- an impossible prospect with the current 1.1.4 release. Apple may simply provide an iPhone OS 2.0 beta release (superseding OS 1.2) to developers. Or it may ship OS 1.2 as a public product, allowing testing for the live-testing of the new components.