Google has been experimenting lot of new things like content on YouTube, including video thumbnails once a video has been completed, cards at the top of searches, video recommendations as notifications, and upgrading the playing screen. Many suggestions were given for YouTube application for Android devices. In YouTube 12.05 they are activating in a phased manner according to suggestions.
In the latest version of the YouTube app, 12.05, the new thumbnail card pops up from the bottom of the app giving you ideas about what you watch next. Each thumbnail can be tapped to bring it into focus and get you started watching something new. Google assumes that this is simply an attempt by Google to divert people from watching current video to another video if they are bored.
This update is not available for everyone on the newest version of the app as it is likely to be only a server-side update that will be slowly made available to all the users in the coming weeks.
The latest version of YouTube is already available on Google Play Store. But, if it is not directly available on Google Play then you can head over to APKMirror and download the file yourself to see if you’ll get these new suggestions when you watch a full screen YouTube video.