Whatsapp has updated with the Material Design of Android 5.0. You will get the new animations and changes of the UI. Beside that the “Phone Calls” function over the app is now enabled with the new update.
You may not be able to find the update on Google Play Store yet but you can download the .apk file manually at: http://whatsapp.com/android/current/Whatsapp.apk
The .apk file size is 19MB and version of 2.12.34