As Ive observed, bitcoin cannot be replaced by another cryptocurrency. Nowadays, bitcoin has become growing daily, increasing its price and demand. It cannot be replace because many are using btc already and attracted to bitcoin.
Do you really believe that?
There was a time when bitcoin was around 1300$. Then is dropped to something like 200$, not it's back around the 1000$ mark.
I do not think bitcoin will disappear in the near future, but you do see, I believe, how unstable it is. Its value, anyway.