I don't think they'll do that. I think their strategy is to see iOS replace OS X for most tasks and users. They will probably pursue a device somewhere between an iPad and a MacBook Air in doing this.

Robert Cringley thinks this will be a display and input device that connects to a phone: http://www.cringely.com/2013/09/19/the-secret-of-ios-7/

I think it will be a standalone device: http://anandabits.com/blog/the-secret-of-ios-7-macbook-vacuu...

The most interesting piece will be to see how Apple approaches this form factor without creating a "refrigerator toaster". I'm optimistic that we'll find out in less than a month...