Not really—with a marketplace, you can choose to buy a product from Store X, or from Store Y. In this future, you'll still have no choice which store you're buying a product from. Apps like Facebook aren't fungible. And if you want Facebook, you'll have to buy it from the Facebook Store, whether you want to or not.

…for publishers. Stores have to compete for software to publish but users don’t get any additional choice when Facebook is only available on the Facebook App Marketplace.

This is a little like exclusives at physical stores but customers have a much less involved relationship in that case.