In theory, it would be cool for studios to have it as an option, but in practice every studio would have to spend extra time on every thumbnail just to keep up with the quality of other studios' thumbnails, and the user experience would be pretty much the same. Maybe you could keep the thumbnails 2D, but make the thumbnail video previews 3D when you hover with the cursor. That way studios wouldn't need to spend extra time on it
Also, how would they work exactly? Like, I see how it could work if the thumbnail is right in front of you, but if it's a video on the top left of the screen, wouldn't DeoVR need to warp the image a lot?