Since 2010, YouTube has supported the uploading of videos with 4K resolution to the platform, and since 2015, 8K is also an option. Until now, a compatible device was enough to play high-definition videos, but this may change soon and require a premium subscription. Users registered for YouTube’s experimental functions on several independent platforms indicated that the 2016p resolution was tied to the YouTube Premium membership both on mobile and desktop.
(source: Reddit) [+]
Whether or not the feature will be rolled out is questionable for now, it could depend heavily on user feedback. Last month, for example, YouTube tried to increase the number of unskippable advertisements, this month you will no longer encounter ten unskippable advertisements in videos. By tying high definition to Premium membership, they could increase the number of paying customers and expand the list of membership benefits. Currently, in addition to ad-free, background playback, YouTube Music and downloadable videos are among the privileges of premium members.