Realistically, I do think it's going to take a heck of a lot to bring YouTube down completely. However, I'm completely in agreement with you regarding the problems that have arisen as a result of recent events and decisions.
Something definitely needs to be done about the Fair Use crisis, because it's just getting out of hand now. It feels like the entire programme is monitored by the Internet's top trolls.
I think this will have a major impact on serious creators and the number of people who make their living on the site - as in, it honestly would not surprise me to see a lot of the big names take their work elsewhere if things continue the way they are.
But when it comes to the audience who are only on the site for free videos, that won't be a problem for them. At the end of the day, no matter how many people stop posting or just up and leave altogether, there will always be something to watch.