After having reading about the possible features in the new Play Store App a few days ago, finally the Play Store 4.4.21 is now available for download, bringing a new interface for the users.
The new user interface replace the old interface, and has a slide out menu that's making the process of discovering and managing Play Content easier on various devices.
The apk file of the updated Play Store is about 5.84 MB, and you can also download the apk file to get the new updated version of the Play Store right now. The download link can be found in the Source link below. Also you can wait for Google to roll out the update, but that would be coming in weeks from now.
As off now only user interface changes have been noticed in the new Play Store app, and other possible changes not been observed yet.Also Android Police notes that " Apk file is signed by Google and it would upgrade your existing Play Store app. Cryptographic als ensures that the file is safe to install was is not tampered in any way".