From a game theory perspective, the worst case scenario you describe is very, very unlikely. Supression of blockchains (if it’s possible at all) would require universal, worldwide coordination, something that just won’t happen. If even a few countries support blockchain, they will benefit so greatly that others will be forced to follow.
We can look to the Internet as an example of how things will likely play out. Despite initial resistance from dicatators, market and competitive forces obligated them to make the Internet available in their country even though it meant their likely downfall. And, just as they worried, it did lead to their downfall—the Internet is credited with contributing to the toppling of dictators all across the world. No country (except North Korea) was able to effectively resist it.
Do you really think that most every country in the world is going to coordinate to enforce North Korean levels of tyranny and control over their populations? I don’t.