From Serguei:

It needs to be fixed in two files:

src/jdk.jdi/share/classes/com/sun/tools/jdi/VirtualMachineManagerImpl.java
    private static final int majorVersion = 9; 9 => 11

open/src/jdk.jdwp.agent/share/native/libjdwp/VirtualMachineImpl.c
  static int majorVersion = 9; /* JDWP major version */ 9 => 11


I also looked at the JPDA/JDI documentation (in closed repo)
and have not found any need for version update there.