While we are at this, I’d share my experience with MOE 1.3. I’ve looked briefly on 1.4, but can’t really move my app to it while it is still being in beta.
Coming from the Java and Android world and having large Java codebase used for both Android and Java-based server backend, MOE was an obvious winner for me to use as a runtime for iOS app. I used all the data models and business logic from Android and Server apps and wrote relatively small Native iOS layer for UI (using XCode 8 UI builder and some manual layouts). Support for cocoapods was especially huge help. The MVP pattern would allow to reuse even more UI logic between Android and iOS.
Now, the down side is the app size and some memory issues (the latter ones I reluctantly ignoring while they aren’t affecting large percentage of my users). But the app size is ridiculous comparing to Android (80Mb+ vs. 7mb). My hope was that this could be somehow addressed in 1.4 and it yet to be seen.
Now, for Kotlin. With Android platfrom support and some of the popular libraries moving to Kotlin it gets increasingly more popular. Kotlin tools already allow to convert existing code to Kotlin on a semi-automated way with decent results. SO, converting Java codebase to Kotlin isn’t a technical problem. With recent announcement of Kotlin-native and corresponding examples  - the platform shows a lot of promise (4.4mb ios binary vs 4mb on android) in both app size and the look and feel of the UI. So, that presents an attractive option for iOS app development.