The government will never allow bitcoin to replace the fiat, or they will lose all their power of manipulation of the financial system. As long as they continue to manipulate the financial system with central banks, the crisis will come in periodically, bigger and bigger, not sure how it will end.
Of course no government will really allow bitcoin to take over their country. It will change the status quo, banking system has been with us for hundreds of year so they won't simply accept it. The sooner that crypto enthusiast accept this fact the better.
That Lehman fall-out in 2008 was really a eye opener because it has affected me a lot. I even opened a thread about it here: (
https://bitcointalk.org/index.php?topic=5028744.0).
We could see though that crypto can be used a leverage for such disaster. If crypto have been in existence that time, I sure that everyone would be happy to move their fiat to crypto to take advantage of its store of value. But to totally say that crypto is going to replace fiat, it won't happen.