Once national currencies have incorporated blockchain tech into their fiat system (even if only nominally) then they can criminalize bitcoin and all non-governmental alctoins as illegal currencies. Of course the corporations don't have any real use for blockchain technology, which is fundamentally contrary to their entire system. That's why they're scared shitless of it and want to squash it.
Is there a single case where a technological happening was completely outlawed after it had been initially welcomed/ tolerated? I can't really think of one.
It's no different in essence than Tor or Bittorrent and they're both perfectly legal.
It's far more acceptable and straightforward to just make it irrelevant by offering more tempting alternatives that are easier to use. The population will go where the gains and convenience reside.