Nothing last forever, and banks are indeed old institution and they will disappear one day definitely. The reason of their disappearance will not be cause they are exist so long, it will be cause they are making rich people richer and they don't care about a little guy, and when awareness get to some higher level banks will be abandoned and people will move to alternatives, and for now fiat have just one alternative, bitcoin!
Wow, that is a very strong statement there mate! I really disagree with you that banks will disappear unless we will be in the point of no world order due to big nature calamities or after most of the countries are destroyed due to nuclear bombs from world war, or any related misfortunes.. But I doubt we will come to that point tbh.