That is going to hurt a lot of people as some were making real good money on Twitch. I am thinking of popular streamers as Xposed, Ayezee, Foss, ... They also stream on Youtube but the go platform has always been Twitch.
Yeah it could be problem for them as they were sponsored gamblers from different casinos to stream and attract more customers to their site giving away promo codes as well but I think they will find some more decentralised platforms where they can stream gambling without any difficulty as Twitch wouldn't support them due to their reasoning of this ban.