First of all, if that Reddit post is really the funniest or stupidest thing you have read in a while, you clearly do not read Reddit much.
Second of all, the guy's post is well-taken, so you can call me one of the stupidest people on this forum if you like. One Hearthstone pro is not going to make the game close down. The point is actually that the game has peaked, people are getting bored of it, and the player-base will eventually start to dwindle.
The most popular Hearthstone streamer has made video with a similar sentiment in the last week.
When I was a kid, everybody played Magic: The Gathering. When I was in high school, Pokemon and Yugioh were very popular. Those games are still around. The games are not dead, and they make a profit, but nowhere near where they were fifteen years ago. I will guess that Hearthstone will still be around five years from now, with the same amount of expansions and everything, but I am willing to bet that the active player base won't be half of what is was at its peak.