With all of the backlash against G+ it's pretty obvious, at least to me, that there will be a migration away from You Tube use. I'm sure you'll see less new channels being started on You Tube and started on other video sharing sites, it's just going to take time. Which site will that be? Who knows, it may not even exist yet. I don't see this happening very quickly, because people are so used to using You Tube, that it's almost ingrained in our society, much like Google has become. It used to be when we needed to look up information, we would go to an encyclopedia, or the library to look through the collections of books, now we "Google" something, just like it used to be "I'm going to share this video with my friends" has become "I'm going to You Tube this."
Once people start breaking free of this mentality, it won't be seen as something to measure success by, personally I've never measured someone's success by how many views they get on You Tube, nor would I penalize them for using another source, but that's beside the point.
At this point You Tube just has a very strong market share of video sharing, but if they keep going the way they are, they will push more and more people away from the service and will be abandoned by everyone but the hard core users, remember MySpace?