I think paper money will not go away. Everyone is not connected to the Internet, and some people can not be connected.
Indeed paper money will not be replaced by bitcoin because it has already build a strong foundation to the people that it was the most convenient way to use for any kinds of transactions that even children know how to use. Money will last forever as it is already long established by all nations.
For sure, there is no reason why paper money should be eliminated in the circulation, it gives majority of the people an ease to transact.
Although digital money is getting more popular now but this two could exist and will share the demand.