They are planning to use swift in the future. Last point: https://ladybird.org/#faq
I don't see that changing any time soon. If Apple truly wanted Swift adoption to be cross platform, they have the resources to do it, but they didn't do it.
That's a key feature of what Apple want Swift for (to gradually replace their C++ projects with Swift) but it's still pretty new. It'll take a while to mature.
Swift is horrible to develop in cross-platform. The language ergonomics are great, but the support just isn't there.
Also - swift is great for lots of applications, but a browser? Why use a garbage collected language for something that needs to be smooth? Unpredictable GC pause jitter is not something you want when smooth scrolling and rendering. Granted Javascript already negates that experience a little bit, but why introduce even more unpredictability?
I get the feeling the leadership loves Mac/Apple, which makes sense in light of their recent iOS announcement. Maybe they're prioritizing that world.