There is no need for eliminate cash the cash will stay there no reason to eliminate cash.
I think its missleading Information like someone had Information and now will change the info to make it look like more bigger more drama and more fear and confuse so its kinda alt media what sells fear... to people but in maximum.
Its just the bitcoin going to be like gold was they made some mistakes in history when the central bank gold was sent to forth knox and stoled from there.... now they have bitcoin wich is far more safe
My conclusion: the cash will stay just the way to create the wealth and money will be changed.
I think its going to go about the way that you've described.
There is no place for maximalism in economy related question.
If (or rather when) crypto is going to take place in global govs backed economy - it is going to be partial at first, thats for sure