It may not be all that likely, but I wonder what would happen if Amazon and Apple collaborate instead of dance-fight?
If Apple is working on an ebook reader it'd be the simplest way for them to take a slice of the pie - just show the reader to Amazon and say "That's a nice ebook business you've got there, it'd be a shame if something were to happen to it."
It depends on how much pie they'd like I guess.