Google Play Store update from 3.7.15 to 3.8.15 is yet to give us a special surprise by introducing Gift cards and Wishlist features. Users will be able to enter a gift card code and redeem the amount.
Google also added the ability to have a balance amount in your account when they started giving away $25 to every Nexus 7 buyer to spend on the Play Store.
Wishlist feature allows us to add an app to purchase in the future when it gets a price drop.
These changes are not announced public, but these are found by Android Police from the hidden APK files.
Source : Android Police