I'm going with Paypal disappearing because bitcoin and Paypal are both used widely on the Internet. In real life, we have banks and we get that cash aren't just going to disappear. they aren't built in hype or some trend anymore. They are built by tradition. The tradition that people have been worshiping money ever since it was created. The tradition that we have to work so hard and get so little in return. And even if we do get a lot fiat money, it's purchasing power is now too little because of the constant inflation going on.

Let's face it. Paypal is what the scammers are using. You see someone here offering his Paypal for your BTC, you better be careful. Even though in the buyer protection policy of Paypal it is said that the buyer can't dispute the payment if it was for a digital good, the scammer can simply just say that he was hacked and he never really had that transaction. We all should use bitcoin but the only thing that's keeping Paypal alive is all the online stores that we use that accepts it and not bitcoin.