Whatever solution I would choose, it has to be something relatively easy to handle, not just for myself but for my non-geek relatives as well. What if the wallet has to be updated or changed? To write a new will is a bit complicated and costly if done by a professional. Paper wallet sounds good but I'm sure someone will come up with an even smarter solution in the future.
it doesn't have to be paper. It can be diamond etched in titanium. You could use electronic storage devices, but they can fail over time.