Magnetic and chip key cards will eventually be replaced by smart phones for cash-like transactions. I think there will still be a place for cash itself, though. Now, although smart phones can conceivably perform this function, they have a few difficulties to overcome.
If I go to the supermarket and elect to pay by smartphone electronic transfer, then I need some way to be sure that I'm paying into the correct account. I need to be sure that the store is telling me the right details and that the person at the checkout is not scamming me by somehow giving me false information. Maybe there need to be several big official signs around the store advertising the correct info.
There's also a problem of trust. How do you know the small shop you visit on holidays won't use the information you leave behind to rip you off? The banks will need to put in safeguards of some kind. If you're connecting with someone else wirelessly, how do you know it's the right device you're connecting to?
Mokalus of Borg
PS - It's probably easiest if it's just friend-to-friend.
PPS - And that we already have.