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.
sourceNow it is absolutely impossible for btc price to fall. If it does, so many people will line up to buy as much as they can and that will push prices up again.
Even exchanges will not allow prices to fall below certain level. It's not free market. We have centralized markets where 90% trade takes place. They are holding big amounts.
Pluse miners will stop mining if price falls below a certain level.