Nice Rab C. Nesbitt picture by the way :)
I think there are more immediate threats to crypto than government regulation/taxation.
1/ The spate of ICOs has significant possibility of causing damage to the credibility of the crypto space if (more likely when) they fail and go pop, all the new investor money that has been sucked into them is going to get scared off, possibly leaving crypto as a fringe place for nutters.
2/ Big businesses co-opt block-chain into closed systems like hyperledger, and this is where all the investment funding starts flowing to.
So for me government issues are only likely if the other two fail to cause significant limitations to crypto-currency growth. The way I see to battle the terror/criminality arguments is through altruistic coins like Gridcoin and SolarCoin, that you can show actually do something positive. The EU Parliament have been presented SolarCoin and liked it.
Also for governments there is the major possibility of offloading a lot of burden onto cryptocurrencies, a lot of admin and beurocracy can go away, and many governments want less friction on trade, so non-national currencies may have a place.
So if crypto doesnt commit suicide, and isnt sidelined by big business, and if it aproaches government with ready made methods to improve their operations in socially responsible ways, then there might be a bright future.