Banks are not going anywhere even if bitcoin gets on the mainstream there will be many people who will prefer to use banks and save their money in it as they feel that banks are the most safest place to save their money which is actually true.
This is true in more economically developed countries but there are many others where you can't rely on banks and in those countries Bitcoin is a better option. So Bitcoin will never make banks disappear if even in undeveloped countries situation will be changing for better, but if in countries like USA or Germany banks become unreliable then Bitcoin might replace them, at least to to an extent.
To an extent? Then bitcoin has already replaced the banks to a really small extend since we are using bitcoins. "To an extent" is such a weak argument in this context.
I still doubt that bitcoins will ever replace the banks. The government is very strict about their fiat currency getting obsolete. When their people are using a foreign currency more than their local currency, the government takes action right away since that will devaluate their fiat currency in addition to the inflation.
The opportunities that exists in the bitcoin world will really help individuals earn more money but the growth of the country in terms of research, technology, nursing, etc. will become slower.