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.
Of course this will be realized. Only this chip will not only be for payment, it will be multi-functional. In the world, the first chips for identification of a person are considered as a priority task for implementation. I think that the payment will be connected to it.