We have seen the 5.0 version of Gmail app for Android a while back. The app has already been included in Android Lollipop update but those of us who are still on KitKat and older versions of Android can now get the 5.0 update, albeit through a leaked APK.
Android Police has managed to get their hands on the APK and uploaded it for the rest of us. As you can expect, the app uses the new Material Design, with a new red bar up top, new hamburger menu, and new compose button. Also, along with the new UI, the 5.0 update also brings with it ability to add accounts from other services, such as Yahoo, Outlook, etc. and not just have Gmail accounts. Your old Email app will continue to exist, however, until you update to Lollipop.
You can download the APK from the source link below.