People always like to say that "Twitter is dying" (and they've been saying that for a long, long time), but I don't think those people realize just how vital of a news source Twitter is these days. I get virtually all of my news intake any given day from Twitter. Also, and I can't stress this enough, no viable direct competitor has even remotely popped up in recent years. It's Twitter and nothing else. Twitter won't even come close to ending until a real, live competitor pops up, and that has not happened yet..
This
I see a lot of things there before it's even reported on the news
If they ever die, the closest one would be Tumblr. I don't think it's backed by anything major? Even if it is, it is reluctant to adapt and will eventually be obsolete. I don't know if Snapchat is a main social media site but I think it'll be the first to burnout. It's kinda a fad