I had the luck of browsing in on YouTube while they were testing their new layout design some days ago. And as you can see from the screenshots, a few changes has been made from the current layout. It seems like they are going back to a white background with no texture and they have also moved the title of the video from above to below.
Notice the user avatar in the comments of the video, a nice addition if they keep it. There´s also a slightly more minimalistic design of the YouTube Flash player, the new does not have the bevel and emboss effect on the control buttons like the current player has.
Clearly, this is just a sneak peak of their work in progress but still, it gives us a hint of what YouTube might look like in 2013. I didn´t see changes on any YouTube channel but that might come too. More customization is welcome now when everybody is locked in with the dull grey layout.