JavaFX is a pretty dead project. Especially on mobile where it has zero users. It actually proves parents point, without Google flutter will be too big. Yes, there will be companies who will pick it up and compile it. That's hard, but doable. The problem is that there's a ton of moving parts. Testing alone is a huge task.

Some companies might pick it but then they would only test the use cases they need or a personal fork. It would also sink without the Google brand to back it.