i wonder: if Bitcoin will become the main coin, what will happen to the money we are using now like us dollar?
Government of any country or state will never accept bitcoin as a main or national currency because of the following reasons.
1) Bitcoin is decentralized having no central authority to control it, government will never allow a currency which is not in their supervision and control.
2) Transactions are anonymous and it will be difficult or impossible for government to check the transaction details of anyone.
3) Taxation issue. It will be difficult to collect taxes from the users over the network.
There will be a relief for the people if government adopt bitcoin as the main coin because it is the most valuable coin of the time and there is a lot of room to earn more profit as compare to the coin of that country and another thing manual taxation system has flaws and there would be an ease to collect the tax online on single click this will give a freedom to user as well as to government.