hmm....in this growing world bitcoin would be uses to pay taxes..

?
most likely it will be taxed to death if governments start to accept it(in the sense to regulate it) more like IRS is doing in the USA
we are lucky that there is not one governments only in this world, at elast we are not 100% centralized, so one can go abroad to trade his bitcoin, where there is no restrictions
It will be very difficult to tax transactions. If bitcoin is to be treated as a currency, then it would be up to the individual to report income or for a business to report a sale and file it in their taxes. Pretty much the same way it's recorded and filed with fiat. For bitcoin to be legitimized, it would need to have the same tax implications as fiat.
A problem would be if it's not treated as a currency and capital gains need to be paid on price appreciation of bitcoin.