We all know that the development of a certain country comes from the taxes of its citizens,
wrong. revenues come from different resources specially in countries with natural resources such as oil rich countries, those with precious metals, ...
and we all know people who engage bitcoin don't pay taxes to the government,
wrong again. in the countries that bitcoin is regulated people are mostly paying their taxes. of course there are always who evade them. but that has nothing to do with bitcoin.
what will happen to a country where 80% of its citizens engage in cryptocurrency?
There is a big possibility that this things might happen In the future because bitcoin is growing faster and very known today.
nothing really. the same way you have to pay taxes for different things now that you are using fiat, by then you will have to pay taxes when using bitcoin in place of that fiat.
if you are paying your taxes now you will be paying your taxed then too. and if you aren't paying taxes now you won't do it then either!