Ron Johnson is Apple's senior vice president of retail and essentially created Apple's hip new retail store presence. Johnson could replace Jobs because, as anyone who's ever worked retail or seen Glengarry Glen Ross, a company always has to be closing.
The bottom line is that moving units is the most important part of Apple's business. And getting people into stores and out with shiny new iPods, iPhones or Macbooks is Johnson's specialty. While he may not have the design or development experience of some of the other Apple candidates, the fact that he can sell should bode well for him.
