Here is a response that might be more specific to the points you raised...
I would seriously doubt it. Even though in western countries I don't think that crypto has necessarily been banned in the majority of the states yet, decentralized ones are certainly not something that historically the governments have been very positive about.
True. Think of gold: Americans were banned from holding gold from 1934 to the 1970s, and both mainstream economists and media have been negative about gold as an investment and as a (potential) part of the monetary system.
But that was because the Western elites don't have enough gold, and the US defaulted on the gold it owed other governments under the Bretton Woods system. If the monetary system were to go back to the gold standard today, based on the gold held by Western central banks and the current size of the money base, the gold price would have to be so high (to keep the new gold standard stable) that it would seriously discredit central bank money.
But the fiat system is fundamentally unstable, so if Bitcoin takes the place of gold, central banks would have the best of both worlds, if they have secretly collected a lot of Bitcoin. (Now I don't think the new system will be exactly like the gold stanard -- for one thing, there will be multiple hard monies. For another, the elites won't repeat anything like the old 'gold is money, and dollar is debt' story that got them into so much trouble over the 20th century -- but that's another topic.)
However, I do see the argument that bitcoin hasn't been killed yet. I think that in a way, regulation has already tightened a lot since its inception to the point that trading has become extremely difficult, but banning bitcoin imho would be unfeasible anyways as it is difficult to enforce and the government would be losing out on a lot of revenue.
As far as I can see, at least in the US, anyone can open a coinbase account and link it to their bank account and start trading. If you hold your coins for a year or more, you get the benefit of being taxed at the low long-term rate. I don't see any serious issue here.
Though banning Bitcoin totally might be unfeasible, such a law would seriously hurt the price. I don't think tax revenues are an important consideration when the elites are dealing with something that can potentially threaten their entire power base (the control of money,) if we go with the conventional wisdom.
Also, I don't see any incentive for them to create cryptocurrencies, which could potentially take control away from the banks and even central banks.
This is the heart of our debate. I totally understand your point, and we have seen it in action with regard to gold. But to re-state my point from a different angle, the elites may well have decided that something like a gold standard (but not an exact copy of it) is actually better for their system than fiat money, as it's more stable and less troublesome.
The total control of money in a fiat system comes with the problem of the incentives for members of the elites to create too much money and debt, and thus long-term trouble. A gold-standard-type system gives the illusion that money is a free market, but really is under central bank control (which was why central banks liked it so much until they ran out of gold.) This type of system is also in keeping with the general style of the Western elites in all areas, e.g. politics and press freedom. A lot of the power of the Western elites comes from the perception (if not the reality) that they promote freedom and property rights of all kinds. They're not afraid of people bad-mouthing them or taking their savings out -- or at least that's the perception they want to cultivate.
But who cares - as far as I'm concerned, even if they've created it for whatever reason which I think is very unlikely, it's still a decentralized platform that is outside of governments' direct reach.
It's surely possible to argue that a (de facto) hard-money standard is still something of a win-win for both the elites and the public, compared to fiat money. We just have to be clear-eyed as to the true nature of any system.