Google announced the new Android design guideline today at the I/O keynote. They are calling the new version L version of Android the biggest release of Android ever. The new design is called Material Design, and will be in the new version of Android as well as other mobile devices and even on the web. Even before the keynote started, Google the intro video for Material Design, which you can view here:
The new design matches leaks of updated apps like Gmail, the Dialer and others that we've seen recently. This new Material Design will be available in the new Developer Preview of Android L. Google knows that this change will take some time to implement. That's why they are making the Developer Preview of Android L available now to devs, instead of waiting until the fall and forcing devs to make the change more quickly. Doing it this way means that developers can bring their apps in line with Google's guidelines before the OS update is available to the general public.
You can find out all about Material Design at Google.com/design. There's a ton of documentation and visuals about the change that's coming, as well programming information for all of you developers out there. Follow all of our Google I/O coverage as the conference happens.