Blizz will not care if streamers are leaving HS, because Blizz showed time and time again (last with the cancel of the tournament mode), that they only care about the absolute low level plebs and new players. Blizz will not react at all and will change nothing! :D
This is true. The Blizzard priority is new players, then returning players, then casual players and drooling idiots, with long-term, invested players last. That type of player craves the next challenge, and Hearthstone has not delivered that. Understandable that many look elsewhere to find it.