GNU Taler is more fit to be the next mainstream way of paying with your phone or online. But it definitely does not replace cash. Not in any privacy sense. It is still digital, and anything digital can and will eventually be hacked at some point. But it's miles better than using my debit card, so I'd always prefer this over my debit card whenever possible. Though if I really want to be anonymous, physical cash is still the way to go. GNU Taler sits somewhere between normal physical cash and debit cards in terms of privacy. I hope it wins.