Beyond that, if we're speculating, a world where all transactions live on a blockchain is an ideal one for a government bent on tyrannical control of the economy. It is likely that governments of the future will have advanced methods of associating wallet activity with real-life activity, especially for citizens who intend to interact with the larger law-abiding economy (if you ask me, blockchain money is the ideal currency for a tyrant). Of course, you can just continue to speculate about future crpytocurrencies that will solve all these issues and that is the reason why this type of speculation gets us nowhere.