We have no plans to move away from Java, but neither will we provide a licensed version of Java. Currently, we are contemplating the following options:
yEd stays on Java 8. Actually, this would be a no-brainer if Java 8 did support display scaling for HDPI devices because aside from that short-coming Java 8 is (at the time of this writing) significantly more stable than Java 9, 10, and 11 which suffer from very annoying problems with regards to printing on Windows and multi-display support on Linux.
yEd is distributed without Java runtime environment. This option is somewhat unlikely, because this is problematic for most yEd users who are no Java experts and should not be required to be Java experts to run yEd.
yEd switches to OpenJDK. While OpenJDK quality has much improved recently, switching will only make sense if Oracle actually fixes the aforementioned problems that make Java 9, 10, and 11.