Hi Thomas,
There are a lot of conflicting stories and misinformation about the health and outlook of JavaFX. The truth is, all of the leads from both Oracle and OpenJDK are reassuring users that JavaFX is alive and well. I like the messaging in this article. Oracle is actively working on JavaFX and contributing to it in the OpenJFX and they are strongly encouraging the community to continue doing the same. In the Java 9 effort to split the JDK into mods, many old pieces that didn't make sense anymore were simply cut. Web Start and Applets are gone. Not JavaFX. Nor Swing for that matter. JavaFX was put into OpenJFX and will remain there and continue to thrive through the community contributions.
Having blabbered on too much about that, I appreciate your preference of Swing with Runtime. At this time, Esri has no plans to engineer anything Swing-specific back into the product. However, as long as developers can continue to bridge Swing and FX for Runtime applications, we will continue to assist as much as we can. The mixing of Swing and JavaFX is more common than folks might imagine.
Good post, Thomas. Please keep sharing your thoughts and feedback!