Personally, I think Apple would be nuts to force Amazon and B&N out of the app store with their draconian 30% Apple tax. But I was one of those who didn't think Apple would allow their apps on the iPad so what do I know?
This could be a ploy to force more book purchases through the iBooks (I think that's the name) app. Since Amazon and B&N can't set prices now because of the Agency 5 collusion they would be forced to take a loss on every Agency book they sold through their app on the iPad.
As of this morning if you look at the top 20 Kindle paid books only 2 of 20 are Agency books with fixed prices. However, of the first 20 books listed on the NYT's bestseller ficiton list 15 of 20 have fixed prices. On any of those Agency books that are sold through the app, Amazon and B&N would have to to hand over 30%. Guess what? 30% is what the Agency books give Amazon and B&N. Amazon and anyone else selling Agency books cannot afford to sell on iOS. There is no extra pie to hand to Apple. Apple would be taking all of Amazon's pie.
What I see is Amazon (and everyone else) negotiating a greatly reduced tax to sell on iOS. I'd rather see them out of iOS completely because any tax like this sets a bad precedence.
BTW, I'm not an Apple hater just terribly disappointed in their products. Even my kids don't use their iPods anymore since it's just as easy to load music and videos on their Android phones. The phones were far, far less expensive than the iPhone. My MacBook only boots into OSX when there is an update, I only boot into Windows since OSX makes it too hard to talk to hardware not officially approved by Apple.