Google announced Android 5.0 Lollipop today along with Nexus 6, Nexus 9 and Nexus Player. The company is gearing up to release a set of preview images of Android 5.0 on October 17th.
In addition to the preview images, the final Android 5.0 SDK that can be downloaded via SDK manager. Google has announced that new Android Lollipop will bring over 5,000 new APIs for developers. Hence, developers can experiment with the new features of Android Lollipop. Once the preview images are available, they can be downloaded from the developer preview page..

http://www.fonearena.com/blog/119215/android-5-0-lollipop-sdk-to-be-available-for-download-on-october-17th.html