All quoted above are true.Bitcoin is now getting more stable than it is before, the adaption of the users are increasing in number and transactions and features were happening in an instant. But still it is not yet absorbed or even heard by atleast half of the worlds population so it will never be imagined that in 15years it will be the universal currency.
Agree. As Bitcoin grows stronger everyday, in development and user acceptance worldwide, we could probably see it become used as a universal currency sometime in the future. However, by that time, Bitcoin scalability would've faced major improvements in order to handle all of the world's transactions. Speaking of which, considering Bitshares capability of handling 100,000 TPS, it definitely shows that it is not too far from cryptocurrencies like Bitcoin to be able to handle superior TPS and become used as a mainstream payment method that would surpass even VISA and MasterCard worldwide. The only thing that I'm concerned with, is whenever scalability solutions like these could affect Bitcoin's decentralization.
Other than that, I think that fiat currencies will stay for quite some time, until cryptocurrencies prove to address above issues.