It is not inevitable but Bitcoin tax is already applied in most of the nations that Bitcoin is legal but regarding the tax percentage then it will depend of what country you belong like in Germany is free of tax, In Japan its 15 to 55% and in France its 19%. I don't know how much in other countries but you may search the google including on how these government applied their Bitcoin tax to the users.
There is no such thing as "Bitcoin Tax" as the only way of identifying what kind of tax your Bitcoin earnings are is the way you earn it and that involves taxes ranging from Capital Gain tax to Income tax, some countries even subject there taxes to VAT for customers paying in cryptocurrency in goods and services. And to correct you, Germany has not completely exempted the tax burden in their country, they only exempt the consumption tax from trading cryptocurrencies as they find it invalid for the field, other taxes still apply in trading such as capital gains tax, you can find out more in this
article.