Doesn't project Catalyst mean that we'd be able to build react-native iOS apps on macOS? :D That would be great, cause with MS support you can build react-native apps on Windows and even Xbox already, just Linux is still out of reach.
From what I understand (although I didn't do much research) all you have to do is to use a new enough version of Xcode and that's it, so React Native doesn't really have to add any support. Ultimately, you build native apps anyway, all JS things are hidden inside.