Traditional retail is becoming increasingly volatile and challenged as a business model. Brick-and-mortar has shifted to online, while online is shifting into pop-up storefronts. Virtual stores in subway platforms and airports are offering new levels of convenience for harried commuters. High Street and Main Street are becoming the stuff of nostalgia. The Big Box is losing ground to new models that attract consumers through their most-trusted assistant—the smartphone. What’s next? What’s the...