Realistically it would take decades, or great strides in usability, for cryptocurrency to really reach the main stream to the point it could be considered a serious alternative for credit cards.
Let’s say OF was forced to switch to crypto payments. They could make the switch tomorrow. Link to a few popular crypto exchanges so that customers know where to buy crypto and Bob’s your uncle.
How long until their customer service system gets flooded with questions about how to use cryptocurrency, and complaints from users who's funds got stolen from XYZ shady exchange.
99% of normal people find cryptocurrency strange and inscrutable, and if you think otherwise you're in a bubble.