"The details on upcoming iPhone OS 4.0 have been leaked and now some of these details are posted on BoyGeniousReport.

Here are some of the details / iPhone OS 4.0 features according to their trusted source;

    * There will be multi-touch gestures OS-wide. (Would make sense for that as the rumored OS for the iPad is close if not the same as the iPhone)

    * “A few new ways” to run applications in the background — multitasking.

    * Many graphical and UI changes to make navigating through the OS easier and more efficient. We haven’t had this broken down, but we can only hope for improved notifications, a refreshed homescreen, etc.

    * The update will supposedly be available for only the iPhone 3G and 3GS, but will “put them ahead in the smartphone market because it will make them more like full-fledged computers” more than any other phone to date. Everyone is “really excited.”

    * The last piece of information is the most vague, but apparently there will be some brand new syncing ability for the contacts and calendar applications.

The upcoming iPhone OS 4.0 firmware is expected to be announced at Apple’s special event  on January 27th"