Negative interest rates are outrageous. Assets that lose value over time are not worth keeping, they are meant for using then. I think if times come when people will lose money for keeping them in banks instead of gaining (at least a little) it will be a demise of current banking system.
No one wants to lose their money, interest will be lessen if banks failed to handle this situations, that will lead finding new ways or options to save money. Investment will be the very best option and aside from real states and insurance crypto also will have a piece of those people who are seeking for new place to put their money. There's a lot of things to consider but chances is open for risky people to find interest in this industry.