So, many people are saying that the majority of the people here are misinterpreting Sakurai. That he is not saying that "the competitive scene will die" and is saying something more along the lines of "a Smash game that focuses solely on competitive play will not be successful". I agree that this is more likely what he is saying, considering what follows after the highlighted paragraph.
However, I'd like to argue against this point.
What Sakurai said would have probably been true back in 2001: if a different company made a game with the exact same physics and mechanics as Melee, but removed the Nintendo characters and said this game is meant to be competitive, I doubt there would be any interest for the game at all.
But in the present day, when Melee has made its mark on Esports by being featured in two Evos and an MLG, interest in competitive Smash has never been higher. In fact, I'd say that any developer who was making a platform fighter would be guaranteed some interest if they said "It's similar to Melee". Even though Air Dash Online is dead, you can't argue that people weren't interested at first when they heard the dev team were fans of Melee and included people like Mew2King. Rivals of Aether is sure to gain some players from Melee (I know I'm one of them) once it's released. If a larger company made a platform fighter and planned to cater to the Melee scene, it would probably have a solid solid playerbase if they did things right. Sure, the numbers will be smaller than the "casual" playerbase, as Sakurai fears, but in return you get a dedicated number of consumers who will look forward to your next game.
Someone might bring up Allstars as an example of a competitive-focused Smash failing, but I'd say that Allstars didn't fail because it focused on competition. There are a lot of horror stories regarding Allstars's functionality as a game. I heard that the super system destroyed character balance, as it screwed over characters without easy combos into supers. I've read a TO's experience with setting up Allstars in his tourney and noted how it had more glitches than Brawl. I'd say that Allstars failed because it was a hamfisted attempt at implementing traditional FG mechanics to platform fighters.
TL;DR Smash as a competitive game does have a future, and its all thanks to Melee.