The gang over at Engadget got invited to an Apple event to launch iPhone OS 3 on 17 March -- a week from today:
We just got the announcement, iPhone OS 3.0 is coming. Set your clocks, mark your calendars. It's going down March 17th. Apparently, we'll get a sneak peak at the new OS, as well as a look at a brand new version of the SDK. Exciting stuff indeed, and we'll be there live at 10am PST (1pm EST) with the liveblog.
Update: This is obviously much sooner than the May-June/WWDC time frame that I've been hearing for iPhone OS 3, but not entirely surprising. Apple appears to looking for feedback on the new OS well in advance of WWDC, so that changes could be implemented before it ships. New iPhone hardware is also rumored in the May-June time frame to coincide with WWDC.
Update 2: Hopefully iPhone OS 3.0 will include all the features mentioned in this rumor by Derek Underwood, i.e. concurrent apps and sandboxing shared-space.
Also, what do you think about Apple settling on "iPhone OS 3 Software?" Sounds kind of awkward, doesn't it? I guess that "iPhone OS" will replace "iPhone firmware" moving forward...
Update 3: MacRumors notes that Apple previously hosted a media event in March 2008 to provide a "roadmap" for iPhone developers, and it appears that this upcoming event may follow a similar theme.