It is quite impossible that the market price of the bitcoin the some with the altcoin falls down because by the time goes by there are a lot of people earning and using the bitcoin and the whole cryptocurrency some of the people made already an investment which they can make a good market income.
Also if we are talking about bitcoin still it has value even there is no market price in terms of USD because they are different. Bitcoin is bitcoin and Usd is USD we cannot change this the reason why the people see the market price is falling because they are using the pair of BTC/USD.
There are people who will always say that bitcoin or other coins will eventually go back to zero but then I believe that it will not happen as long as there are people who uses it to invest or trade. It's a normal thing that the price fluctuate since it is volatile.
That's the reason why are the people invested and the bitcoin market price becomes volatile. We saw already how does the bitcoin falls and this is good opportunity to bought a lot and a good market income.