As much I'd like to think a lot of people are going to jump into playing US2, I bet more than half of the people who watched them play are just there to, well, watch. Its like the one Youtuber I like watching, FrankieOnPCin1080p, he made an episode of ARK: Survival Evolved.
The video has like 2M views, yet the amount of people playing at any one time has never gone above 50-60k since it came out.
No doubt it will bring more people, but how much it brings in is another story. Only the devs will know if it will have any substantial effect.