LoL will never die. Its an easy game designed for casuals. Even if all of the hardcore/semi-hardcore players leave the influx of new players will only be slowed down slightly
People already prophecied 5 years ago that WoW would die because it was getting more casual with every patch, and the game is still going strong
I dont know why people are upset over this since it has absolutely no impact on Dota whatsoever
Dota managed to become big and build an Esports with nothing but the support of the community. Even if Riot completely absorbs the online game market I dont see Dota being affected by this.
Especially because China is the biggest market for Dota, and LoLs presence in China is non existant.