Microsoft will let developers of many apps downloaded sign up for early access to the sdk of Windows Phone 8. Smaller developers have to wait for the public release of the sdk. When that will be is not yet known.
The sdk must allow that in any case the most popular apps for Windows Phone 7.5 is already optimized for the new version. Developers of less popular apps will have to wait until a not specified later time.
Microsoft keeps the new features of WP8 under the cap, and she wants to keep that a secret by the sdk are not openly online. It is unclear when Microsoft Windows Phone 8 as a whole wants to go show. An earlier version of the sdk leaked all out.
Despite the fact that Windows Phone 8 has not yet been presented, there are already devices announced that use the new operating system. Nokia revealed last week the Lumia 920 and 820, two weeks ago presented the Samsung Ativ S.
Windows Phone 8 has indeed largely the same interface as Windows Phone 7, but it is, nevertheless, a whole new operating system. The kernel, and multi-engine are the same as in Windows 8, while support for nfc, sd cards, multi-core processors and 720p screens is added.