Google's Play Store update this thursday (v3.8.15) looked exactly the same as the previous version, but included 300 kilobytes of extra code and resources. The folks at Android Police did a software teardown and came up with evidence that "inarguably points to … redeemable Play Store gift cards." Photos of the packaging for these cards surfaced yesterday at Android Central, so it's likely they'll be available soon.
The update also showed evidence of a forthcoming wish list feature, so apps, books, TV shows, movies, music, and magazines can be stored for later purchase. It's unclear how (if at all) this might differ from a "shopping cart" - or why you'd put off buying content if you have a saved balance - but we're sure some users will find it convenient.
What do the updates mean? Mostly that the Play Store will work a little more like Apple's iTunes store. (iTunes gift cards have been available since the iTunes store first launched over nine years ago.) Google Play won't lose any features in the transition, so it's really only becoming more convenient.