Updates to the Play Store are not often particularly exciting, and this update is really much of the same. Play Store 5.4.12 has been spotted in the wild, and the always-enterprising folk of XDA have grabbed the APK and posted it to APK Mirror for everyone to take a look at.
The short version is we don’t know what’s inside that’s markedly different to 5.4.11 that was posted a couple of days ago, and 5.4.10 posted a few days before that. We have noticed some visual changes of late, but those aren’t from 5.4.12; they’ve been around for a week or two now.
Still, if you must have the bleeding edge, you can grab the latest APK from APK Mirror and let us know what you find.