It'll never happen. Amazon got big and rich from making clever decisions, and this one would be glaringly stupid move for them. The idea of having to stock and operate stores seems to be a cash hole as opposed to having a near perfect mail order system.
The idea of a kiosk with a sample Kindle and a computer setup for on-the-spot ordering would be a winner. Hmmm, I may need to work a deal with eBookwise.....