As to what might replace it, UK publication Campaign believes that YouTube will make more extensive use of the six-second unskippable video ad instead. While unskippable ads in any length are annoying, six seconds is a lot better than 30. Campaign also notes that any ad shorter than 30 seconds can be made unskippable, so you may still run into fairly long 20-second commercials still. But still, it seems like a pretty tacit admission that users aren't willing to wait that long to get to videos. We'll take it.