During today's keynote, Apple released several new apps into the App Store under their developer account. The apps are all stock iOS apps that presently come pre-installed under iOS 9.
The list includes:
If you try to download an existing iOS app, the "Get" button is greyed out, indicating you already have the app. Several readers have confirmed that you can now delete these apps in iOS 10, and later redownload them from the App Store. Apple could also choose to upgrade the apps from the App Store rather than waiting for iOS updates.