According to Reddit and Twitter reports, Google is testing a new design for the YouTube homepage. The design seems to be focused on making content more prominent, with larger thumbnails. A direct result of their larger size is, of course, the fact that you can see far fewer videos at a glance compared to the current design.
Another interesting change to the presentation of videos on the YouTube homepage in the new design is that the videos are no longer grouped together by the channel or topic. Instead, they seem to just flow one after the other. On the one hand, the change will give more real estate to video thumbnails to draw in viewers. On the other hand, the reduced density of videos will mean you have to scroll through your YouTube feed more.
In a statement to The Verge, YouTube confirmed it's experimenting with the a change and said it was "currently testing a new homepage layout to improve the watch experience for our users.” This would suggest that the redesign is not yet a done deal, and the company will be looking at user feedback to assess the viability of rolling it out at a larger scale.