Here are some scenerios that can cause the price of btc to fall drastically. (In my opinion, it is highly unlikely and the possibility very slim).
(1) No way to trade bitcoin or exchange it for goods and services.
(2) All governments of the world placing a ban on bitcoin and bitcoin related activities making it highly illegal.
(3) The entire bitcoin network and nodes going offline making it impossible to even make underground transactions in bitcoin.
(4) Another crypto overtaking bitcoin and value and more people shifting investment to this new crypto.
sourceItems [2] and [3] are practical sounding reasons, but [1] and [4] are completely meaningless. Even when the organizers called for the referee to blow the whistle to the whole thing to stop bitcoin, it still cannot go beyond the limits of decentralization. People are not slaves, when there is no more democratic freedom, it means the world is in darkness as well. bitcoin will still be worth a specified amount. it still fluctuates!