Yup, honestly Twitter and Snap will be fine. What will totally go out of business is Meta. Instagram is the last stronghold for Meta and any teenager I speak to are more excited about Tiktok than Instagram.
I have my doubts about this. Facebook have 2.9 billion active users, and Instagram has about 2 billion, and that are a lot of users to show ads to earn money. Meta will stop growing, but I doubt it will go out of business in a lot of time.
One of the way to continue growing would be monetizing WhatsApp (that has 2 billion users currently) in any different way to what they actually are doing (using users' data).
TikTok ads are all video based afaik. Since video ads are more "valuable" I totally get how that could give them a nice boost over twitter or snapchat as they grow.