The Visa debit antitrust fight raises a bigger payments strategy question: what actually competes with a Visa debit transaction? The answer matters for routing, Durbin, pay-by-bank, alternative rails, network economics, and the platforms deciding how money moves.

Reported discussions about major U.S. banks exploring a Fiserv debit-network deal are more than banking gossip. If large issuers get closer to the debit rails, the economics underneath Durbin, least-cost routing, debit network incentives, and flat-rate pricing arbitrage could get a lot less predictable for ISVs, PayFacs, platforms, processors, and merchants.