First, just have to collapse all the shares before the dollar itself will collapse. Therefore, to go to the fact that the first thing, with the destruction of the entire financial system, will collapse, I would not recommend.
You should think that if a dollar collapses, the entire financial system will collapse and cryptocurrency will not save anyone. Reality will live well China, which today is buying up all the gold and silver, and selling Bitcoin to fools. After all, no one today will doubt that almost 70% of all Bitcoin transactions are controlled by Chinese miners.
Well the ending days of 2017 and the starting days of 2018 had been good in terms of profitability and the reason behind the profitability was that Bitcoin and ETH had been high. Now in the past few months, we know it had big decline in its values and has its market affected as well. Expectations about the surge in 2018 end and in the start of 2019 are high but it is something that you just cannot predict. So many invisible forces affect the market.