Sure, crossplatform will let you build for more platforms in a smaller timeframe, however, they have their own set of problems. Crossplatform tools have been around for some time now and since the beginning people say they will replace native. Today, that has not happened. I think they can coexist. Some apps fit crossplatform really well, others have to work around its limitations. Most definitely you won't match the performance using react.
I think the kotlin team has looked or wanted to look into kotlin on ios, but I don't know what the current state is.