Appreciate the article and the topic, but I'd argue againt many of the points made.
1. Snapchat's video (Discover) content is not really all that social. Discover can be completely avoided by users just wishing to connect socially. It's also very high production value, as the content is made by professionals not amateurs. Short-form mobile-sized (vertical) video, as evidenced by TikTok (amateur production value), is coming fast thanks to low attention spans and a phone in every pocket.
2. Instagram only TEMPORARILY regained relevance with Stories. Snapchat never NEEDED stories, it was a shot across the bow aimed at Finstagram's hold on public-amateur content. But the beach-head has remained, particularly with the younger set; so, as the platform age I expect Finstagram properties to struggle to keep their monopoly on public+amateur content. TikTok is a MAJOR problem for FB.
There's much fundamental analysis missing from the mass-media's portrayal of this long-term battle. Instagram merely fought back and won a small battle to prevent a total rout of their business in record time. But over time, it should prove impossible to move from public-facing content platform to private-trusted content platform.
People not learning the lessons from this war, will not have a chance other than luck.