When Bitcoin will be universally accepted accepted by Government, of course it will be taxed accordingly. Do you think it will still be as in demand as it is right now, that makes its price higher and higher everyday.
Does the bitcoin community is ready for this?
No. that is very impossible. The reason why many people got interested to the bitcoin is because of being decentralized. The government can't control the bitcoin and it can't be taxed.
Nothing is impossible for the Government If they want something they could get it. If Bitcoin gets legally accepted by a country, Government would impose such laws and regulations on transacting Bitcoin. There's no such thing as a free entry into the market without getting taxed. To add Government can manipulate everything.
To answer the question, We are already taxed due to transactions fees. But once the government started to play a part in this industry for sure above that transaction fee is another tax imposed by the Government itself. The demand will depend on how will Bitcoin react at the market. We all know that Bitcoin is volatile, if it continues to grow then demand would increase for sure. But, potential investors would limit their investment to avoid big losses not only because of the tax but to make sure that they will not engage in something beyond their control.