Maybe it will decrease but this is normal tax policies as everyone in the world are paying tax from fiat earnings so i think it shall be the same in Crypto currencies earnings too. This is the consequence if we want Bitcoin will be declared legal in a central country in which it will require every citizens to pay Bitcoin tax as income tax but this is no issue to me as long as the Bitcoin users will be fully protected specially from the scam investments.
I don't think that it should have an adverse effect on crypto. Many people hate taxes and would rather avoid it but it should not badly have an impact to the market. It's not surprising to have tax policies eventually, it's bound to happen anyway especially since there will be mass adoption by other countries. Since it will be also expected that people will just choose to evade these taxes, it's not a surprise that tax enforcement has been made. I don't think that this will negatively affect Bitcoin. This just spells some trouble for the tax evaders.