What's an agency model? Why, it's the 70%/30% split between platform and content provider currently used in the App Store, and the same model that's planned to be used in iBooks on the iPad. And it's important to note that this is exactly what Jobs said would happen -- that publishers would move away from Amazon when they had another system to go with.
What we don't yet know is where prices will end up on the iPad -- Jobs said that prices would be "the same," and it's looking more and more like the $9.99 bestseller price is going to be abandoned for $14.99 or even higher. But that's only because Amazon is fighting shadows with the iPad right now. If they can actually woo some content back to their side when the iPad actually releases, we may see prices get a little more competitive. Until then, the iPad hasn't even come out and it's already shaking up the ebook industry completely.