It is impossible to even imagine that when the iPhone was launched, there were no apps and no App Store. In fact, all that the first gen iPhone had were a bunch of out of the box apps developed by Apple and a browser. It was only later that Apple opened up to the third party apps and a dedicated App Store, which has become one of the charms of owning an Apple made iPhone or iPod Touch or iPad.
Looks like, this time when Apple adds a new product vertical, it would not be wasting any time in bringing a dedicated App Store as well as open the SDKs for third party devs to bring their own apps for the iWatch. The iWatch is expected to be announced in a day on September 9th and there has been a lot of interest around what Apple would do with its smartwatch. One of the features of the watch according to 9to5Mac report is the support for third party apps and a store to select apps from. If true, it would be interesting to see whether the number of apps available for iWatch would already be more than the competing Android Wear devices.
The report seems to have substance as it bases the assumption of the presence of an App Store, because Apple had recently seeded the SDKs for wearables of some of the common apps such as Facebook to their developers. If this is true, you can expect a lengthy demonstration of apps on iWatch at the keynote tomorrow. The SDK seeded has deep integration with other iOS 8 features such as Healthkit, Handoff etc according to the same report.
Make sure you do not miss the Live unveiling of the next gen iPhone and iWatch by checking out the live stream.