Ever since back in the beginning of the year around January, Google has been working on completing a UI refresh for Google Play on the web interface which we started to see appear in early 2015. Slowly but surely Google continued to roll these visual changes out to users across the globe, with more appearances of the updated web interface design popping up for other users again in June, and now it looks like Google may be rolling out the UI tweaks to all users globally. The new UI doesn't change too much in the looks department, but it does better evoke Google's vision of material design with the card style interface for items shown on screen.
Some people may not be seeing these changes just yet and that is likely going to be a common thing since Google tends to roll changes out in stages for most of their updates. The new UI should also have a slimmer card style box in the middle of the screen with a collection of smaller thumbnail size cards that sit along side the main box of whatever app, game, movie card etc. the user is viewing. Based on the images above and below, it's evident that the UI changes are here, and the UI can appear in a couple of different ways with the main card showing in the middle alongside the smaller thumbnail size cards, or the thumbnails can appear at the bottom of the page if there isn't enough space in the window you have open.
Buttons for installs and seeing more apps also appear with a slight roundness compared to before the visual changes but that's more of a relatively minor alteration compared to the overall tweaks Google has made to the design. In just a matter of days, Google will have finally updated both the Android Play Store app as well as the Google Play web interface for users. This isn't something you can update on your own, so you just have to sit tight and wait until Google flips the switch on their end for each region that has access to the Play Store on the web, which shouldn't take too long now.