An eMarketer forecast suggests that Twitch could reach 40 million viewers in the United States by 2021.

Twitch’s growth could lead to major revenue for some of the site’s biggest names.

Other streaming sites such as Mixer and Facebook Gaming may have to fight much harder to beat Twitch.

A forecast by eMarketer has suggested that Twitch will reach 40 million viewers in the United States by 2021. It means 15.5% of U.S. digital video viewers will be enjoying Twitch streams by the end of 2020. But it will still have to contend with rivals such as YouTube, Mixer and Facebook Gaming, the eMarketer forecast points out.

eMarketer forecasting analyst Peter Vahle also said that non-gaming content could be a major part of Twitch’s growth. This content, which includes music streams and streams in the “Just Chatting” topic, “began driving significant traffic in 2019,” said Vahle.

Twitch’s growth could funnel much more money to the site’s top streamers. More people watching ads means more revenue for these streamers, and as Twitch has just rolled out a new ad system, viewers are less likely to leave the site due to frustrating interruptions.

It could also mean more money for streamers who don’t want to stay on Twitch. Sites such as Mixer and Facebook Gaming have been spending millions on getting streamers to use their sites. It seemed to begin when Mixer got Ninja to leave Twitch.

Since then, Facebook Gaming has also gotten Disguised Toast and Corinna Kopf to leave Twitch. It’s unclear how much the streamers were paid, but it’s unlikely to have been small.

If other streaming sites feel like they need to do more to take on Twitch, then they could be willing to spend more to get streamers to leave the site. Twitch streamers may also need to be given much more money for them to leave.