What do you mean "if"? Most governments are already beginning to tax it, and given the fact Bitcoin won't go away and "die" the others will join as well it is only a matter of time. To your second point, I don't think that hinders the growth of the community, if anything I believe it helps it in an indirect way. You see the biggest sharks and sharps in the world won't enter the market because it is unregulated and they don't want to put millions on unregulated exchanges. If all the exchanges become regulated, sure it may stifle growth a little in the short term, but in the long term I think it is in all our best interests because the sharks will enter knowing the exchanges are 100% regulated and secure from fraud.
Thats true. Im not sure why people think that you do not have to pay any taxes for bitcoin. In fact, the IRS has expounded on how you still have to pay taxes for every bitcoin transaction you make and even just for holding. More details here from CNBC crypto:
https://www.facebook.com/cnbccrypto/videos/1612209732195600/This may not discourage the holders though. It only legitimizes holding btc so this wont scare them anyway so long as they still get profit. I would honestly prefer to pay taxes rather than having to deal with a crypto ban in my country. Its likely, however, that most hodlers are just evading.