Suppose you woke up tomorrow morning and found that Bitcoin had dropped to 0$, or that Bitcoin had disappeared or been scammed. How will you be at that moment?
Bitcoin is not dollars, so Bitcoin cannot be $0. What you meant I believe is if the dollar value of bitcoin is 0. Then, it means that each and everyone of us will have plenty bitcoin then.
I would say I'll buy more, but it might not be possible because bitcoin will have no dollar equivalent. But if we can buy with gold or other assets, I will have to accumulate more bitcoin and we will start again.
That scenario will happen if there is zero demand, but is it really possible?