When the dollar collapses, the price of bitcoin will explode overnight 
SMH....IF the dollar collapses, we won't have any need for Bitcoin because everyone will be broke.Secondly, Bitcoins are not "worth" $100. $30-$50 is still extremely high for something you can't spend.
money isnt value its self, its simply a proxy for value. having money become worthless doesnt make the vegetables in your garden worthless, or the furniture in your house, or your car. those things will still exist and a new medium of exchange will rise to facilitate trade. That medium will act as a proxy for the same value that the dollar used to act as a proxy for.
The thinking that life will go on as normal if the dollar was to collapse, is just silly. Things go bad for the dollar, they go bad for everything else, including Bitcoin. Even if Bitcoin had the chance to fill a void as big as the dollar would leave, it still couldn't remotely handle the task, given its extremely low transaction/second rate. Thats the Bitcoin Achilles heel, that everyone pretends doesn't exist. Bitcoin can't even compete with Visa's transaction capabilities. How do you expect it to replace the dollar?