in my opinion it is still a bit necessary, what if you got somewhere and there is no internet or electricity but you still need to pay for something?
if there only were cryptocurrencies for wich you need internet to send a transaction then you would be stuck to buy the thing that you would want or need in that situation
I think if that time comes that digital currencies are already adopted,the government then will also be aware that it needs internet connection for a successful transaction.Surely they will find ways for that maybe putting up wifi in every areas so that people will find it easy to transact using digital currencies.