Just this month alone, a revamped UI, a new trending section, Netbanking support for India, changes to search results, and minor tweaks to app installations have all shown up for some users. This latest change was first spotted in June, but appears to be rolling out to even more users.
Left: Previous Top Charts UI. Center, Right: New UI.
The new lists do away with the spacing between cards, and more prominently shows the ranking of the top applications.
New interface for Play Store Top Charts rolling out to more users was written by the awesome team at Android Police.