A new version of Google Play Store with version 4.4.21 is now rolling out globally to all Android devices. It features a new slide-out navigation menu. Though the update is rolling out globally, you may not receive it at the moment. It usually takes a few weeks for the update to be live for every Android user in the world.
However, Android Police has uploaded the APK for us to download and you can install it just like any normal APK. You only need to make sure that you have checked “unknown sources” option in Settings>Security. Also, the apk has a cryptographic signature so you can be sure that it has not been tampered with. The slide-out navigation is the only addition with this version and it has the following options: Store home, My apps, My wishlist, and Redeem, in addition to “Shop” at certain times.
via Android Police