For me I do not think that there is coming a big surprise for the paper money in the world because paper money will always be the number one paying method for the most people so i do not think you should worry about that.
Paper money is very hard to determine what is going to be its future. But still that is not a problem because people tend to use paper money.
And I don't think paper money is going to be out of the league when bitcoin gets popular at all.
It will exist forever in my opinion because that is the simplest means to use in all kind and forms of transactions, you can easily use it anywhere with the need of power and internet.
Forever? You hesitantly think that it will not be obsolete for a certain time? Giving the fact that we're making our progress in a futuristic era. There will be a high chance that the paper money will be removed once we already had a techno-world.
We can't really say that paper money is going to exist forever there is no such permanent thing in this world.
And I'm quite sure that paper money will lose soon because of bitcoin.
That is never possible, paper money will always exist, do you expect labors, maids, and poor people will accept their payments in bitcoin, they will prefer paper money for sure.