Im thinking like an micro chip implanted in our body. This system is not out of the picture because how we discover things every year, it is not impossible that in the future this things may happen and it will boom like btc.
No one is going to accept to have a chip implanted in their bodies just to make some payments, so the payment system that you are describing is not going to come to happen, besides people already have their smartphones with them all the time and you can use crypto thanks to them.