If it's any of them, YouTube is going to give them a run for the money. There are 3 things that will need to happen for Big Red to loose:

1. Content creators will need to reach braking point.
2. YouTube fails to make nice.
3. The challengers get a better interface. YouTube has a bunch AI, intelligent search, and recommendations. A way to filter out non native language videos would be a start.

It's early days and I have faith that thing s will improve, I just causious optimism.