American Express is running a pop up Centurion lounge in Manhattan next weekend. They want to be where their customers are, and they want to be where their customers are shopping.
Other pop ups have foretold where they wanted to offer a permanent lounge. For instance they had a pop up at LAX before getting a deal done to build a lounge there. They did a London pop up and then announced a London Heathrow Centurion lounge.