"YouTube files bankruptcy and closes it's doors because people aren't willing to watch advertisements and executives could think of no other source of revenue to keep the doors open."
That's never going to happen, because the executives would be fired for incompetency. If advertising suddenly becomes a non-viable revenue stream, YouTube (and internet video hosting in general) is not going to disappear.
In fact, I ACTIVELY WISH we would drop the advertising model, and I will not support it if I have any alternative. It is a poison on the world and a giant economic waste. The world would be much the better place if YouTube (and the internet in general) gave up on advertising entirely.