IntelliJ does use JNA quite extensive, already, on the Mac. It wouldn't be a stretch to imagine more extensive use of JNA e.g., for custom widgets.

JetBrains guys are very smart (I dislike Java as a language, but I continue to be impressed by IntelliJ) and I have no doubt they'd be able to switch a native layer if needed: they have all the motivation to (it's a commercial product).