Don't know.  It may be one of several world reserve assets... Along with precious metals and critical resources such as water and energy.  I mean, we're talking LOOONG game here.  Liquidity/volume is an issue.  Some counties/corps won't have enough but will have other assets that will be highly desired to trade with each other.  Easily? Not as much. But you better believe a drought stricken region will trade critical elements for water, or gold will be traded for energy, etc.  

To be the sole reserve currency (roughly $13T) it's estimated each coin would have to be worth $722k in today's USD.  Thus, a country like China wouod require 25% of supply.  There are 195 countries.  Somalia has the weakest known reserves of about $17M.  BUT! Those coins ain't available... Unless 6102 style games get played.  So as market values rise you better believe they'll look to other options (as they are with BS stable coins and legislation).