If a law was created focusing on the tax aspect on bitcoin, then expect its prices to be controlled and regulated at some point.
That makes no sense. The government doesn't care about the price at all, they just want to build a framework that will give people enough (forced) incentive to pay their taxes, which is the most logical path to follow for them.
This framework is getting more shape by the month. It won't take long before they have completely regulated this market, allowing no room for tax evasion. If you think you can outsmart the government in that aspect, you'll pay for it.
Centralized exchanges are nothing more than a toy for authorities. Coinbase functioned as primary example of how you can't ignore the drastically changed market ~ they suffered a major loss by snitching on 13,000 users.
It's nasty, but at the same time understandable because they had to comprise one way or another. 13,000 users with likely the highest balances have now something to think about, and hopefully they'll learn from their mistake.