That's a high single-event number. Do the numbers sustain across the year? MLB and NBA have over 100 events per year (considering all the days games as one daily "event")
Also, for the people that age out it seems like 3 more people join. Search viewership growth for games like League of Legends, Dota2, and CSGO and you will see that watching videogames is serious business.
If you include people watching in the client itself it is a bit closer but still Twitch would be double or more.