The App Store Review Guidelines are pretty clear that how we do extensions on Android would not be allowed on iOS. In fact, I think Apple has gone so far as to neuter the dynamic code loading functions at runtime (all external libraries must be linked in the binary reviewed by the App Store team). However, we are considering that eventually we could allow for extensions in compiled apps by linking the extension's binary code at compile time. That would be functionality we would have to implement later as I do not want it to hold up the iOS buildserver general release.