I don't think if a currency legalized in a country it won't have a tax deduction I am sure it is have a tax deduction when you pay or buy something using bitcoin. And I think it would be easy to the government to put the tax deduction in any transaction of bitcoin if that's gonna happened in the near future.
When bitcoin become universal and the whole world start using only bitcoin and there is no other currency in the market, people will feel ease and happiness because they will be able to use their coins all over the world without any bank transactions and exchanging. They will easily use their wallets for payments. People will enjoy cashless society.