how could people say that bitcoin is about to cease existence?
It's not surprising to see these kind of FUD articles/posts every time the Bitcoin price starts going sideways or stagnates for a long time. It's probably the only time trolls have a reason to start spunning nonsense by writing bitcoin obituaries and whatnot. Best advice would be to ignore those posts and articles you read online, don't feed the trolls.
If it can survive an 80% drop, surely it can survive the drop this year, right?
Absolutely. If anything another drop could mean that a rebound is bount to happen soon and prices will shot up.