Here's our own (and MacCast's) Adam Christianson's proposal: Apple Maps could pinpoint locations accepting Apple Pay. Fire up Maps and search for the nearest location of, for example, Portland chain Burgerville. You search the map and find locations, and if there is a particular type of pin, you know it's a place that accepts Apple Pay. See our mockup below:
A TMO mockup of how Maps pins could include Apple Pay.
Another way this could work is to integrate it into the Yelp information. Anecdotal evidence shows that it is easier to update Yelp information than Apple Maps info, so when a business starts accepting Apple Pay, including that information on Yelp would be easy. With the integration Yelp has with Apple Maps, it would be a good way to get more people to use the info panel in Maps, which could look something like this TMO mockup:
TMO mockup of Yelp including Apple Pay.
This could be a great thing for businesses which are local but don't draw headlines for accepting Apple Pay the way national chains can. At least a few people are already making buying decisions based on where Apple Pay can be used, so this would only make it easier. It could even be a filter on Apple Maps. Hopefully as time goes on and Apple Pay becomes more common (as do devices that are capable of Apple Pay), this is something that can become a reality.