Actually there is already an app in the app store according to this blog post.
And as far as I know two of facebook’s apps have been built using react-native (maybe not completely ): Groups and Paper.
So if you have any concerns, whether react-native is production ready: I think if Facebook can use it in their production apps it’s probably good enough for you too … ( no offense ) 😀
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solved React Native – why is so few apps in AppStore? [closed]