Banks has a lot of function that bitcoin cannot replace... Even if bitcoin go mainstream, we can never see it replace banks, banks are not just into holding and releasing money, they are more than that... Bitcoin wallet is clearly like bank book or ATM, and as I've mention, banks has a responsibility and function more than that.,..
Nope, post offices still operates nowadays... It looks like that it is close, but it is not... Most of the time they are now delivering mails from the government and transactions like that, and some goods coming from customs which needs to be taxed and needs tariff... But anyway, if it is possible as you said, I think that means we need to transact our deed of sale and land title in the bank with a bot in the computer? that's too impossible... I am sure that it's far from happening...