I think if bitcoin legal in this world it will be great currency of all transaction and the investors getting more bitcoin because of the financial and benefits for the everyday so it is very exciting if can happen.
perhaps the entire system will be much improved and the use of crypto currency will be in any sphere of human activity. But each user of crypto-currencies, as well as everyone who earns on this business, will have to pay certain taxes from each transaction.
Actually, legalization of bitcoin have a lot of advantages that makes us comfortable and easy to used by the different features of bitcoin can have. Also, it may also used on crime since the bitcoin is decentralized it will take advantage to those bad people that their money will using to transfer via BTC. Thus, it will depends to those users which make sense to each and everyone of us here in the crypto currency community.
The fact, even Bitcoin is ilegally in some countries or the large country as China, but a lot of people still want to hold and buy it as much as possible. I agree with you Bitcoin becomes legal will help the activity of Bitcoin in that country will be smooth than normal. However, Bitcoin is legal or illegal, the criminal still using it for their transactions. I think so.