But current Windows Phone 7.5 users will not be able to upgrade to the full Windows Phone 8 release. Instead, Microsoft plans to roll out for these users a "7.8" release that will feature the most visible OS change: a revamped Start screen that gives users the abilities to dramatically change the size and colors of the distinctive Windows Phone tiles. With both versions of the OS, users will be able to shrink and expand tiles much larger and smaller sizes, or organize the layout of tiles as they see fit.

The first Windows Phone 8 handsets will be available later this year, worldwide, initially from HTC, Huawei, Nokia, and Samsung, according to Microsoft.

Microsoft finally will address an array of IT issues with Windows Phone, changes that may spur adoption of Windows Phone in the enterprise market. The new trusted Windows core components will be coupled with Microsoft's data encryption and Secure Boot technologies. Enterprise will also be able to create and securely distribute their own Windows Phone apps, via a private cloud or internal apps "store" without having to make use of the online Marketplace site.

Finally, Microsoft says Windows Phone 8 will "support" mobile device management tools. There were no other details but it seems to mean either a new API that can be used by third-party mobile device management vendors or some sort of extensions that allow applications that manage Windows PCs to also manage Windows Phone handsets.

The next generation of Windows Phone devices will be the first with multi-core CPUs. The first crop of new devices this fall will be dual-core handsets on "next generation" Qualcomm silicon. Currently Windows Phone 7.5 supports one resolution, of 800 x 480 pixels. But the new OS version also add two high-definition screen resolutions: 720p (1280 x 720 pixels) and WXGA (1280×768). Existing Windows Phone 7.5 apps will run smoothly without any additional changes on the new phones, even on the higher resolution displays.