Android 5.0 is mysteriously called "L" at the moment and is described as the "biggest release to date" of the operating system.
It's defined by bold colors, fun animations, and a "flat" design aesthetic. Looks like Android is finally catching up to iOS in terms of design. Like iOS, Android L has a bright color scheme. The interface seems to disappear into the content with transparent layers.
See more preview pictures of the operating system here.