"We'll see P2P payments continue to displace paper checks," McKee said. "Checks could become extinct in another 10 to 15 years. The impact on cash will be less dramatic."
Some P2P apps, like Venmo, could evolve into full-scale mobile wallets, which might be what Apple foresees.
"You could pay a merchant directly via your P2P app, completely circumventing the payment networks" which have been built up over decades by banks and credit card companies and many third-party companies, McKee said.
"The attractiveness of this approach to merchants is apparent, since it would result in reduced fees" that merchants now pay to banks for credit-card transactions, McKee added.
One implication of McKee's futuristic scenario is that big banks could be working with Apple on a P2P mobile payment scheme in order to avoid being cut out of their share of future transactions.
Apple wouldn't comment on any plans for P2P mobile payments.